A  DAY  IN  THE   MOON 


From  a  drawing  by  the  Abbi  Morcitx. 

THE  EARTH  AS  SEEN  FROM  THE  MOON. 

(The  landscape  shows  part  of  the  range  of  the  I,unar  Alps.) 


[Fronlispixe. 


A  DAY  IN  THE  MOON 


BY  THE  ABBE  TH.  MOREUX 

Director  of  the  Bourges  Observatory 


WITH    40    ILLUSTRATIONS    FROM    PHOTOGRAPHS 
AND    DRAWINGS 


Mew 
FREDERICK  A.  STOKES  COMPANY 

PUBLISHERS 


PRINTED    IN    ENGLAND 


ANNtA 


CONTENTS 

CHAPTER                                                                                                                                                t   f  PAGE 

I.       THE    MOON               .             .          :';•''  .             .  I 

II.        OBSERVATIONS    OF    THE    ANCIENTS            4  8 

III.  THE     MOON     AS     SEEN     BY      THE     NAKED 

EYE       .  y,             .                           .    •                       .  27 

IV.  WITH    THE    EYE    AT    THE    TELESCOPE       .  45 
V.       ON    THE    WAY                     .   ,                       .              .  66 

VI.       LUNAR    LANDSCAPES     .             ."          .             .  82 

VII.       ON    THE    MOON     .             .             ,"«j         .              .  103 

VIII.       THE       MOON,      THE      TIDES,      AND      THE 

CHANGES    OF    THE    WEATHER     .         JAi  1 2O 

IX.       THE  MOON,  VEGETATION,  AND  ORGANIC 

LIFE                  ?    .                       "    .             .              .  137 

X.       ASTRAL  INFLUENCES  AND  ASTROLOGERS  153 

XI.       THE     ACTION     OF     THE     MOON     ON     MEN 

AND    ANIMALS            .     .    '.     .             ,             .  1! 


vi  CONTENTS 

PAGE 

LIST  OF  348  OBJECTS  SHOWN  ON  THE  MAP  OF 
THE  MOON  DRAWN  BY  THE  ABBE  MOREUX 
(CRATERS,  MOUNTAINS,  AND  INEQUALITIES 
OF  THE  SURFACE)  .....  184 

OBJECTS    TO   BE   STUDIED    ON   EACH   DAY  OF 

THE  LUNATION        .....      190 

LUNAR  ELEMENTS  .....  192 
LIST  OF  THE  PRINCIPAL  LUNAR  <e  SEAS  "  .  195 
CHIEF  CHAINS  OF  LUNAR  MOUNTAINS  .  .  196 

INDEX  .......        197 


ILLUSTRATIONS 

The  Publishers  are  indebted  to  the  kindness  of  the  Author  for  the  loa»  of  many 
of  his  original  drawings  for  reproduction  in  this  English  translation. 

THE   EARTH   AS    SEEN    FROM    THE   MOON  .  .  Frontispiece 

FACING   PAGE 

THE  NORTH  HORN  OF  THE  MOON        .....  l6 

EARTH-LIT  NEW  MOON      .          .         .  30 

THE  MOON  AT  THE  FIRST  QUARTER  (AGED  7  DAYS  3  HOURS)       .  34 

THE  PHASES  OF  THE  MOON          ......  36 

THE  MOON  (AGED  8  DAYS  23^  HOURS) 38 

THE  FULL  MOON   (AGED  14  DAYS  I   HOUR)           .  40 

THE  MOON  (AGED  20  DAYS  19  HOURS)          .          .  42 

THE  MOON  AT  THE  LAST  QUARTER  (AGED  23  DAYS  8  HOURS)     .  44 

SUNRISE  ON  THE  MOUNTAIN  RING  "  WALTER  "       .         .  48 

HEVELIUS  AND    HIS   WIFE   OBSERVING    T!!E    POSITIONS   OF   THE 

HEAVENLY  BODIES      .......  58 

THE   MOON         .........  60 

COMPARATIVE   SIZE   OF   THE   EARTH    AND    THE    MOON            .             .  76 

A    GAP    IN    THE   MOUNTAIN    RAMPART   OF   COPERNICUS         .             .  82 

OUTLYING    BUTTRESSES    OF   THE   LUNAR   ALPS                 ...  84 

COPERNICUS       .........  92 

PERSPECTIVE   VIEW    OF   A    LUNAR    MOUNTAIN-RING   .             .             .  IO2 

REGION    OF   THE   LUNAR   APENNINES        .....  IO6 

RF.GION    OF    THE    "  MARE   SERENITATIS  "  1O8 


vn 


viii  ILLUSTRATIONS 

FACING  PAOB 

EXAMPLE  OF   THE  CREVASSING   OF  A  HARD  SURFACE CLEFTS 

NEAR  TR.IESNECKER      .          .          .          .         .         .         .112 

THE  "STRAIGHT  RANGE"  PRESENTING  THE  APPEARANCE  OF  A  SWORD   114 
ASPECT  OF  THE  "  MURUS  RECTUS  "  (THE  "  STRAIGHT  RANGE  ") 

OF    THE    MOON    .  .  .  .  .  .  .  .Il6 

CONJECTURAL    FORMATION    OF   THE   UNSEEN    SIDE    OF   THE    MOON       Il8 
DIAGRAM  TO  ILLUSTRATE  THE  ACTION  OF  THE  MOON  ON  THE  TIDES    I2O 
REGION    OF   THE    "  MARE   VAPORUM  "     .  .  .  .  12<f 

INTERIOR   OF  A   LUNAR   VOLCANO  .  .  .  .  130 

A   CLEFT    IN    THE    MOON*S    SURFACE    NEAR    HYGINUS  .  .136 

THE    NORTHERN    HORN    OF   THE    MOON  .  .  .  .138 

THE  EDGE  OF  THE  MOON   LIGHTED  UP  BY  THE  SETTING  SUN  .        142 

THE   MOON'S    SURFACE  .......        148 

REGION     BETWEEN     THE     "  MARE     IMBRIUM  "     AND    THE     NORTH 

POLE    OF   THE    MOON  .  .  .  .  .  .154 

THEOPHILUS,    CYRILLUS,   AND    CATHERINE          .  .  .        l6o 

IN   THE   TEXT 

GALILEO  GALILEI  (AFTER  THE  PORTRAIT  BY  LEON l)  .          .          .  II 

THE  FIRST  PICTURE  OF  THE  MOON  DRAWN  BY  GALILEO  .         .  14 

METHOD  OF  MEASURING  THE  HEIGHT  OF  A  LUNAR  MOUNTAIN    .  l6 

DE  RHEITA'S  MAP  OF  THE  MOON  (A.D.  1645)  .         .         .  51 

CYRANO  DE  BERGERAC's  FLIGHT  TO  THE  MOON     ...  67 
DIAGRAM  ILLUSTRATING  THE  DISTANCE  OF  THE  MOON  FROM  THE 

EARTH         .  .  .  .  .  .  .  .79 

SKETCH-MAP  SHOWING  THE  SIZE  OF  "  COPERNICUS  "  AND   "  MAURI- 

LYCUS "     .  .  .  .  ...  .  .  .87 


A  DAY  IN  THE  MOON 

i 

THE   MOON 

To  launch  out  into  space,  to  rise  ever  upwards,  to 
leave  the  Earth  far  away  and  fly  on  strong  wings 
to  the  Moon,  to  descend  upon  its  silvery  surface, 
traverse  its  unknown  plains  and  valleys,  examine 
in  detail  the  structure  of  that  globe  which  we  see 
suspended  above  our  heads,  and  at  last  to  come 
back  and  tell  the  people  of  the  Earth  the  daring 
adventures  of  that  distant  journey  .  .  .  what  a  dream  ! 

We  have  all  had  such  dreams  on  some  autumn 
evening  when,  as  we  returned  in  thoughtful  mood 
from  some  long  walk  in  the  country,  the  thin 
crescent  of  the  new  Moon  rose  on  the  background 
of  the  sky,  still  tinted  with  the  twilight  glow. 

And  this  reminds  me  of  an  evening  in  one  of 
the  vacations  I  spent  in  the  Sologne,  my  native 
i 


2  A   DAY   IN   THE    MOON 

district.  I  had  accompanied  my  father  on  one  of 
those  walks  of  which  he  was  particularly  fond,  and 
during  which  he  never  missed  an  opportunity  of 
developing  my  interest  in  the  various  phenomena 
that  Nature  is  each  moment  placing  before  our 
eyes. 

Behind  us  the  sun  had  set  and  night  was  coming 
on  with  a  perfectly  clear  sky.  We  were  walking 
along  a  footpath  among  clumps  of  heath  and  furze. 
A  herdsman  was  singing  as  he  slowly  brought  back 
his  cattle  to  their  shed,  and  gradually  as  the 
night  came  on  the  thousand  sounds  of  Earth  were 
hushed.  One  might  have  said  that  Nature  was 
assuming  a  recollected  silence  the  better  to  prepare 
man  to  feel  the  charm  of  the  heavens  that  were 
soon  all  studded  with  stars. 

And  now,  as  the  tints  of  the  landscape  faded  away, 
my  childish  imagination  was  full  of  delight. 

The  wide  unbroken  plain  extended  to  the  hori- 
zon, which  it  seemed  to  touch,  and  I  thought  that 
the  sea  must  present  much  the  same  appearance. 
Here  and  there  the  thickets  of  high-growing 
shrubs  stood  out  in  dark  patches  on  the  ground,  and 
I  imagined  they  were  like  great  waves.  The  clumps 
of  pines  scattered  here  and  there  farther  off,  black, 


THE   MOON  3 

ill-defined  masses  rising  over  all  else,  seemed  to  me 
to  be  big  ships  with  their  masts  swaying  gently  in 
the  light  evening  breeze. 

Suddenly  a  glow  like  that  of  a  fire  gleamed  out 
beyond  them,  the  ruddy  disc  of  the  full  Moon  rose 
above  all  the  things  of  Earth,  and  immediately  my 
mind  was  prompted  to  other  thoughts. 

Why  is  it  that  the  Moon  does  not  always  appear 
to  be  round  ? 

What  is  the  explanation  of  its  phases  ? 

I  knew  that  with  the  naked  eye  one  could  only 
have  a  very  rough  idea  of  its  aspect,  and  I  had 
often  levelled  at  its  shining  disc  a  telescope  of 
very  moderate  power,  the  only  astronomical  instru- 
ment then  in  my  possession. 

Those  greyish  spots  that  one  sees  with  the 
naked  eye  appeared  more  clearly  defined  even  with  a 
magnifying  power  of  only  ten,  but  my  telescope  was 
hardly  powerful  enough  to  show  me  the  lunar  craters 
and  mountain-walled  plains.  I  thought  indeed  that 
I  could  catch  glimpses  of  them,  but  nevertheless  I 
was  always  ambitiously  dreaming  already  of  more 
powerful  instruments. 

I  used  often  to  ask  myself  at  that  time  if  it  was 
true  that  the  Moon  was  strewn  with  giant  mountains, 


4  A   DAY   IN   THE   MOON 

that  a  man  could  walk  and  stand  on  its  surface  and 
photograph  its  landscapes  ?  And  those  "  craters " 
that  had  been  discovered  in  our  satellite,  had  they 
really  been  volcanoes  in  earlier  ages  ? 

If  man  had  existed  in  the  times  of  the  Brontosaurs 
and  the  Iguanodons,  would  he  have  been  able  to 
make  out  the  jets  of  fire  and  smoke  in  lunar 
eruptions  ? 

Why  did  this  heavenly  body  revolving  around  us 
always  present  the  same  appearance  since  man  first 
observed  its  enigmatical  surface  ? 

On  our  Earth  generations  succeed  each  other. 
Man  has  spread  over  and  peopled  the  globe.  And 
each  evening  the  tillers  of  the  soil  returning  to  their 
farms  look  up  to  the  sky. 

At  the  hour  when  in  the  cities  of  civilised  lands 
artificial  light  blots  out  the  stars  and  deprives  the 
town-dweller  of  that  spectacle  of  the  universe,  the 
countryman  can  gaze  on  the  starry  sky,  and  he 
always  asks  himself  the  same  questions  without 
making  any  attempt  to  solve  them.  At  school 
he  is  taught  to  divide  up  the  Earth  into 
separate  compartments.  He  learns  by  heart  the 
exploits  of  blood-stained  heroes.  He  knows  the 
date  of  the  battle  of  Crecy,  when  for  the  first  time 


THE   MOON  5 

cannon  made  their  appearance  hurling  their  deadly 
bolts.  He  is  told  of  the  properties  of  explosives 
and  the  principle  of  the  bullet  in  the  modern  rifle. 

And  those  who  possess  riches  no  longer  live  in 
contact  with  Nature.  Fashionable  gatherings,  plays, 
race-courses,  theatres,  are  the  chief  interest  of  their 
aimless  and  unprofitable  pursuits. 

The  literature  of  the  day  reflects  this  idle  and  use- 
less life.  Most  of  our  works  of  fiction  display  in 
the  full  light  of  day  the  blemishes  of  a  decadent 
Society,  and  under  the  pretext  of  psychological 
analysis  describe  the  disorderly  outburst  of  passion. 

There  is  material  and  industrial  progress  every- 
where, and  this  is  a  good  thing,  but  moral  progress 
does  not  keep  pace  with  it.  Men  neglect  the  study 
of  Nature,  and  lose  touch  with  its  manifestations, 
which  are  capable  of  leading  them  infallibly  to  a 
consideration  of  the  great  questions  of  science  and 
philosophy. 

Since  the  days  of  the  Egyptians  and  Greeks  and 
the  other  peoples  of  antiquity  with  whom  our  civili- 
sation began,  the  mass  of  men  have  remained  quite 
ignorant  of  the  great  questions  which  are  alone 
worthy  to  occupy  a  thoughtful  mind. 

Man,  bowed  to  the  Earth,  no  longer  looks  upon 


6  A   DAY   IN   THE    MOON 

the  Heavens  and    no   longer  pays   homage  to   his 
Maker. 

Question  a  thousand  of  the  inhabitants  of  our 
planet  and  ask  them  where  they  are  in  the  universe, 
speak  to  them  of  the  Solar  System,  of  Jupiter,  of 
Saturn,  or  of  the  stars — hardly  one,  at  most,  will 
understand  you  and  grasp  the  fact  that  there  are 
other  subjects  of  interest  beyond  that  of  our  trifling 
daily  occupations. 

From  the  astronomical  point  of  view  nearly  all  of 
them  have  remained,  so  far  as  this  goes,  not  at  the 
epoch  of  Pericles  or  Augustus,  but  at  that  of  the 
Stone  Age. 

And  meanwhile  what  wonderful  progress  has  been 
made  by  all  the  physical  sciences  in'general — progress 
by  which  Astronomy  has  been  the  first  to  benefit. 

We  can  now  answer  questions  of  which  the 
solution  once  seemed  to  be  a  thing  of  insurmountable 
difficulty. 

The  discoveries  in  physical  Astronomy  have  told 
us  more  and  more  of  the  marvels  of  far-off"  worlds. 

And  as  for  those  that  lie  nearer  to  this  Earth  of 
ours,  we  are  able  to  examine  them  with  magnificent 
instruments.  They  are  part  of  our  own  system,  and 
are  linked  with  our  lot  in  the  universe,  and,  to  adapt 


THE   MOON  7 

the  saying  of  an  ancient  philosopher,  "  nothing  that 
concerns  them  ought  to  be  without  interest  for  us." 

Science  has  in  a  measure  realised  that  dream  of 
visiting  worlds  so  different  from  our  own,  thanks 
to  the  penetrating  power  of  the  instruments  it  places 
at  our  disposal. 

We  can  now  enter  on  detailed  studies  of  each  of 
the  planetary  bodies,  and  as  the  Moon  is  of  all  the 
lights  of  the  firmament  the  one  nearest  to  us,  it  is 
natural  to  begin  our  excursions  in  the  heavens  with 
this  neighbouring  world,  which  the  laws  of  attraction 
link  with  our  planet  by  bonds  as  subtle  as  they  are 
mysterious. 


II 

OBSERVATIONS   OF   THE  ANCIENTS 

WHATEVER  may  be  said  to  the  contrary,  it  is  not 
at  all  certain  that  the  powers  of  the  human  intelli- 
gence have  made  any  very  notable  progress  since 
the  first  appearance  of  man  on  the  Earth. 

We  have  no  doubt  that  there  were  among  the 
ancients  men  of  superior  intelligence  from  every 
point  of  view,  and  the  study  of  their  writings, 
their  pursuits,  their  theories,  is  well  calculated  to 
throw  a  new  light  on  our  recent  discoveries  and 
at  the  same  time  help  us  to  realise  the  imperfection 
of  our  knowledge. 

When  it  is  a  question  of  studying  a  science,  the 
only  acceptable  method  is  that  of  following  its 
development  and  its  evolution  through  the  various 
periods  of  history.  Such  a  method  will  at  once 
show  us  that  each  science  grows  like  a  living 
creature.  Each  important  step  of  progress  is  always 
the  outcome  of  long  preparation,  and  never  comes 


OBSERVATIONS   OF   THE   ANCIENTS      9 

suddenly,  just  as  in  the  living  organism  the  useless 
elements  are  got  rid  of  and  give  place  to  new 
substances. 

We  shall  have  many  examples  of  this  in  the 
course  of  our  familiar  talk  about  the  science  of 
the  Moon,  or  as  it  has  been  called,  Selenography. 

Without  speaking  of  the  dreams  of  mythology, 
that  assigned  to  the  Moon  the  personality  of  Selene 
or  Diana,  and  told  how  the  Nemean  lion  came 
from  our  bright  neighbour  to  terrify  mortal  men, 
it  is  very  interesting  to  examine  the  opinions  of 
the  ancient  world  about  our  satellite  in  times  when 
the  telescope  was  a  completely  unknown  instrument. 

Achilles  Tatius,  who  wrote  three  centuries  after 
Christ,  has  recorded  for  us  the  opinions  of  his 
immediate  predecessors.  For  some  of  them  the 
Moon  was  merely  a  detached  fragment  of  the  Sun — 
in  days  nearer  our  own  Laplace  could  find  no 
better  theory.  According  to  others,  it  was  formed 
of  exhalations  from  the  earth  which  took  fire  in 
the  upper  regions  of  the  heavens. 

In  a  passage  of  his  translation  of  Plutarch,  Amyot 
tells,  quoting  a  disciple  of  Aristotle,  how  the  latter 
held  that  "the  forms  and  images  of  the  great  sea 
of  the  Ocean  appeared  in  the  Moon  as  in  a  mirror." 


io  A   DAY    IN   THE   MOON 

Many  of  the  ancient  philosophers  had  remarked  the 
connection  between  the  phases  of  the  Moon  and 
its  position  with  respect  to  the  Sun,  and  this  idea 
of  comparing  the  Moon  to  a  mirror  had  become 
current  among  them.  So  the  author  just  quoted 
says  that  "  in  its  polished  brightness  it  is  the  most 
beautiful  and  clearest  mirror  in  the  world." 

All  these  fancies  were  very  far  from  reality,  and 
the  first  astronomical  telescopes  were  destined  to  give 
some  astounding  surprises  to  the  old  astronomers. 

The  telescope  was  not,  it  is  true,  first  invented 
by  Galileo,  but  it  is  to  this  man  of  science  that  the 
honour  belongs  of  having  been  the  first  to  apply 
the  instrument  to  the  study  of  the  heavens. 

There  can  be  no  doubt  of  this,  and  Galileo  him- 
self tells  the  story  in  his  Sidereus  Nuntius^  which 
appeared  in  March  1610  : 

"About  ten  months  ago  I  was  informed  that  a 
certain  Dutchman  had  devised  a  telescope,  by  means 
of  which  he  saw  distant  objects  as  plainly  as  if  they 
were  near  at  hand.  This  instrument  had  already 
been  used  to  make  a  number  of  experiments,  to 
the  results  of  which  some  gave  credit  while  others 
denied  them. 

"  And  this  was  confirmed  for  me  some  days  later 


OBSERVATIONS  OF   THE   ANCIENTS     n 

by  a  letter  which  the  Frenchman,  Jacques  Badovere, 
addressed  to  me  from  Paris.  All  this  finally  led 
me  to  devote  myself  entirely  to  studying  the  means 


GALILEI  GALILEO 
(1564-1642). 

After  the  portrait  painted  and  engraved  in  1624  by  Ottavio  L.eoni. 

of  arriving  at  the  application  of  a  similar  device  ; 
and  I,  in  fact,  succeeded  therein  shortly  after,  with 
the  help  of  the  theory  of  refraction.  First  of  all, 
then,  I  made  a  leaden  tube,  to  the  ends  of  which 


12  A   DAY   IN   THE    MOON 

I  fitted  lenses,  both  of  which  had  one  plane  surface, 
while  the  other  side  of  one  of  them  was  convex  and 
that  of  the  other  concave.  Then  bringing  my  eye 
to  the  concave  lens,  I  saw  objects  looking  near 
enough  ;  these  objects  appeared  three  times  nearer 
and  nine  times  larger  than  with  the  unassisted 
sight. 

"  I  then  made  a  more  carefully  finished  instru- 
ment, which  magnified  the  objects  more  than  sixty 
times. 

"Finally,  sparing  neither  trouble  nor  expense,  I 
succeeded  in  making  for  myself  an  instrument  so 
excellent  that  it  enabled  me  to  see  objects  a  thou- 
sand times  larger  than  with  the  unassisted  sight." 

With  regard  to  the  magnifying  powers  of  which 
Galileo  here  speaks,  we  must  go  into  some  details 
that  are  necessary  for  the  understanding  of  this 
somewhat  ambiguous  passage,  and  which  will  make 
clear  the  meaning  of  an  expression  that  frequently 
recurs  in  dealing  with  astronomical  subjects. 

Take  a  square  of  which  each  side  is  an  inch  in 
length  and  double  these  linear  dimensions.  What 
shall  we  have  ? 

Each  side  of  the  new  square  will  be  two  inches 
in  length,  and  the  surface,  which  originally  measured 


OBSERVATIONS   OF   THE   ANCIENTS    13 

one  square  inch,  will  have  become  2x2  =  4  square 
inches. 

Thus,  in  doubling  the  linear  dimensions  one 
quadruples  the  surface  ;  if  one  lengthens  the  sides 
threefold,  the  surface  becomes  3x3  =  9  times 
larger. 

It  has  now  been  long  an  established  rule  in 
physics  that  the  magnifying  power  of  instruments 
is  always  to  be  stated  in  linear  units.  When  we 
speak  of  a  microscope  magnifying  twelve  times,  we 
mean  that  in  the  object  under  examination  each 
dimension  appears  twelve  times  longer. 

Galileo,  doubtless  to  strike  the  imagination  of 
his  contemporaries,  purposely  had  recourse  to  the 
method  adopted  by  certain  dealers  in  optical  in- 
struments, who  advertise  microscopes  magnifying 
1 44  times,  but  carefully  omit  to  add  "  super- 
ficially " — the  corresponding  linear  magnification 
being  only  twelve  times. 

This  principle  applies  to  objects  of  other  forms 
than  a  square,  as,  for  instance,  a  polygon  or  a 
circle. 

Galileo's  first  telescope  magnified  the  surface  nine 
times  ;  that  is  to  say,  three  times,  estimating  by 
linear  units. 


A   DAY   IN   THE   MOON 


Later,  it  is  true,  he  constructed  instruments 
magnifying  the  diameter  of  celestial  objects  thirty- 
two  times  ;  that  is  to  say,  32  x  32  =  1,024  times 
superficially. 

These  instruments   are   now   kept  in   one  of  the 

museums       of 
Florence. 

Galileo  was 
at  Venice  when 
he  heard  of 
the  discovery 
of  the  tele- 
scope. He  at 
once  returned 
to  Padua, 
where  he  held 
a  professorship 
of  Mathema- 
tics, and  it  was  there  that  he  constructed  his  first 
instrument  with  lenses  that  he  happened  to  have 
in  his  possession. 

Later  on  he  presented  a  telescope  magnifying 
thirty-two  times  to  the  Doge  Leonardo  Donati,  and 
then  another  of  the  same  kind  to  the  Grand  Duke 
of  Tuscany. 


THE  FIRST  PICTURE  OF  THE  MOON. 
DRAWN  BY  GALILEO  IN  1610. 


OBSERVATIONS   OF   THE   ANCIENTS    15 

The  Venetian  Senate,  in  its  admiration  for  his 
invention,  confirmed  him  for  life  in  his  professor- 
ship at  a  salary  of  i  ,000  florins  a  year  ;  and  the 
Grand  Duke  of  Tuscany  lavished  gifts  upon  him. 

"  It  would  be  superfluous,"  continues  Galileo,  in 
the  passage  already  quoted,  "to  reckon  up  the 
advantages  to  be  obtained  by  the  use  of  this  instru- 
ment on  land  as  well  as  at  sea.  But  leaving  aside 
these  terrestrial  things,  I  have  directed  my  researches 
towards  the  heavens,  beginning  with  the  Moon." 

And  what  Galileo  saw  might  well  excite  the 
wonder  of  his  contemporaries. 

He  first  of  all  discovered  mountains,  more  or 
less  brilliant  spots  and  circular  hollows,  which  he 
compared  to  the  eyes  in  a  peacock's  tail. 

At  the  moment  of  the  phases  the  boundary  be- 
tween the  dark  part  and  the  light  appeared  to  him 
under  the  form  of  an  irregular,  uneven  line,  and  he 
drew  from  this  the  logical  conclusion  that  the  Moon 
was  far  from  being  a  perfectly  smooth  sphere.  But 
then,  how  was  one  to  explain  the  fact  that  at  the 
moment  of  Full  Moon  the  margin  showed  neither 
projections  nor  hollows  ? 

For  this  question  Galileo  found  two  answers — 
which  were  incorrect.  He  said  that  either  the  Moon 


i6 


A  DAY   IN   THE   MOON 


had  an  atmosphere  which  enlarged  the  apparent 
size  of  its  disc  and  made  its  marginal  irregularities 
disappear,  or  else  the  mountains  seen  in  perspective 
concealed  each  other. 

In  reality  he  ought  to  have  noted  that  only  when 
an  object  is  illuminated  from  the  side  it  throws  a 
shadow  that  makes  its  summits  stand  out  and 

reveals  its  irregularities. 

With  our  actual  tele- 
scopes the  outer  edges-  of 
the  Moon  are  far  from  being 
as  regular  as  they  appeared 
with  the  telescopes  of 
moderate  power  in  use  at 
the  beginning  of  the  seven- 
teenth century.  We  have, 
however,  to  thank  Galileo 
for  having  noted  another 
and  a  very  important  phenomenon,  which  put  him 
on  the  track  of  an  ingenious  method  of  measuring 
the  height  of  the  lunar  mountains. 

On  account  of  the  surface  of  the  Moon  being 
convex,  when  the  sun  rises  upon  one  of  its  regions 
the  rays  first  light  up  the  lofty  summits  of  the 
mountains.  An  astronomer  looking  from  the 


METHOD  OF  MEASURING  THE 
HEIGHT  OF  A  LUNAR 
MOUNTAIN. 


THE  NORTH  HORN  OF  THE  MOON. 

(Reversed  image.) 


16] 


OBSERVATIONS   OF   THE   ANCIENTS    17 

Earth  sees,  therefore,  a  luminous  spot  separated 
from  the  bright  part  of  the  Moon  by  a  dark 
band  corresponding  to  the  valleys  still  plunged  in 
shadow. 

But  under  these  conditions  it  is  easy  to  take  the 
line  of  a  solar  ray  as  a  tangent  to  the  curved 
surface  of  the  Moon  ;  this  straight  line  touching 
the  mountain  summit  forms  with  two  lines  drawn 
to  the  centre  of  the  moon  (one  vertically  through 
the  summit,  the  other  from  the  point  where  the 
ray  first  touches  the  curved  outline  of  the  moon) 
a  right-angled  triangle,  of  which  the  length  of  the 
sides  can  be  ascertained.  Then  a  simple  calcula- 
tion gives  at  once  the  height  of  the  illuminated 
summit  (which  is  equal  to  the  difference  between 
the  two  lines  drawn  to  the  centre  of  the  moon). 

The  study  of  the  shadow  thrown  by  a  lofty 
peak  would  lead  to  the  same  conclusions,  and 
since  the  time  of  Galileo  astronomers  have  not 
failed  to  improve  and  perfect  these  methods. 

But  however  this  may  be,  it  is  certain  that  in 
1610  there  was  a  complete  revolution  in  accepted 
ideas  as  to  the  nature  of  the  Moon.  Thanks  to 
Galileo's  discoveries,  it  became  impossible  to  deny 
that  our  satellite  presented  the  appearances  of  a 


1 8  A   DAY   IN   THE   MOON 

world  in  many  ways  resembling  the  Earth,  and 
with  a  surface  standing  out  in  higher  relief  in 
certain  regions. 

But  did  this  miniature  of  our  planet  possess  seas, 
rivers,  and  forests  ?  Was  it  inhabited  ? 

This  was  something  that  could  not  yet  be  de- 
cided by  observation,  and  the  savants  of  the  time 
could  give  free  rein  to  all  the  fancies  we  permit 
to  romancists  and  poets.  Such  a  fine  chance  was 
not  lost,  and  voyages  to  the  Moon  supplied  to 
authors  a  subject  all  the  easier  to  dilate  upon 
because  there  was  a  complete  absence  of  positive 
facts. 

But  was  Galileo,  as  is  so  frequently  stated,  the 
first  to  distinguish  the  mountains  of  the  Moon  ? 

History,  as  has  often  been  said,  is  nothing  but 
a  perpetual  beginning  again.  Was  this  compara- 
tively recent  invention  of  instruments,  that  make 
objects  appear  nearer,  anything  more  than  a  re- 
discovery, and  are  we  to  believe  that  the  ancients 
were  entirely  ignorant  of  the  use  of  magnifying 
glasses  and  even  of  some  kind  of  telescope  ?  This 
is  a  question  that  we  may  examine  together  before 
closing  the  chapter. 

Anaxagoras,  according  to  the  account  of  Diogenes 


OBSERVATIONS  OF   THE   ANCIENTS    19 

Laertius,  asserted  that  there  were  mountains,  valleys, 
and  inhabitants  in  the  Moon. 

This  passage  has  generally  been  regarded  as  a 
piece  of  mere  fancy,  but  who  can  say  whether, 
when  he  wrote  these  lines,  the  author  of  the  Orphic 
poems  was  not  echoing  an  old  tradition  that  came 
from  Egypt,  Phoenicia,  or  Chaldaea  ? 

The  best-established  scientific  ideas  can  be  lost 
as  the  old  civilisations  were  ;  and  it  seems  to  me 
interesting  to  give  here  the  results  of  a  study  I 
made  some  time  ago  of  this  little-known  chapter 
in  the  history  of  Optics  among  the  ancients. 

First  of  all,  was  glass  known  to  the  peoples 
of  antiquity  ?  This  point  appears  open  to  no 
doubt. 

There  is  a  passage  in  the  writings  of  Aris- 
tophanes in  which  he  relates  that  in  his  time  globes 
of  glass  were  sold  by  the  grocers  in  Athens.  At  a 
later  date  Pliny  tells  how  the  immense  theatre 
erected  at  Rome  by  Scaurus,  the  son-in-law  of 
Sylla,  which  could  hold  80,000  spectators,  had 
three  sets  of  seats  rising  above  each  other,  and 
those  of  the  second  series  were  entirely  covered 
with  mosaics  in  glass. 

In    the    seventh    book    of   his    Recognitions    the 


20  A   DAY   IN   THE   MOON 

pseudo-Clement  relates  a  legend  of  St.  Peter  having 
gone  to  the  island  of  Aradus  and  seen  there  a  temple 
with  columns  of  glass  of  extraordinary  height  and 
thickness,  which  excited  his  wonder  even  more  than 
the  splendid  statues  by  Phidias  with  which  this 
temple  was  adorned. 

Seneca,  in  his  Questions  on  Nature?  speaks  of  the 
phenomena  of  the  colours  seen  when  one  looks 
slant-wise  through  the  projecting  angles  of  a 
piece  of  glass.  At  this  time,  therefore,  the  prism  and 
the  production  of  colours  by  refraction  were  known. 

In]  the  reign  of  Nero  cups  of  cut  rock-crystal 
were  in  use.  The  tear  bottles  found  in  the  tombs 
are  also  made  of  glass,  and  at  this  period  it  was  on 
glass  globes  that  the  celestial  spheres  and  the  con- 
stellations were  marked  out. 

In  his  Optics,  Ptolemy  inserts  a  table  of  the 
refraction  of  a  ray  of  light  in  passing  through  glass. 
Now,  the  indices  of  refraction  given  in  our  modern 
works  on  Physics  approximate  so  nearly  to  his, 
that  we  must  conclude  that  the  glass  of  his  time 
differed  very  little  from  that  which  we  make  nowa- 
days. 

1  Quastionum  naturalium,  libri  vii.,  the  only  surviving  Roman 
treatise  on  physics. — Translator's  Note. 


OBSERVATIONS   OF   THE   ANCIENTS    21 

All  these  are  certain  facts.  But  it  will  be  said 
that  they  do  not  prove  that  the  learned  of  antiquity 
knew  the  properties  of  lenses. 

Granted  ;  but  here  is  some  other  evidence. 

Everyone  has  heard  of  the  emerald  through 
which  Nero  watched  the  games  of  the  amphitheatre. 
Aristophanes  in  his  comedy  of  the  Clouds  makes  a 
curious  jest.  In  the  play  Strepsiades  explains  to 
Socrates  the  possibility  of  setting  fire  to  com- 
bustibles by  means  of  a  glass  globe.  And  this 
ingenious  person  tells  how  he  has  found  a  way  of 
avoiding  the  payment  of  his  debts  by  thus,  from  a 
distance,  destroying  the  acknowledgments  in  the 
hands  of  his  creditors,  without  their  being  able  to 
find  him  out. 

The  Romans,  who  had  learned  science  from  the 
Greeks,  instead  of  caustic,  used  globes  of  glass  ex- 
posed to  the  sun  for  cauterising  flesh.  And  if  the 
Vestals  negligently  allowed  the  sacred  fire  to 
become  extinguished,  it  was  their  duty  to  rekindle 
it  by  means  of  the  heat  of  the  sun  concentrated 
through  little  glass  spheres. 

When  in  1 905  I  was  sent  by  the  French  Govern- 
ment to  Tunisia  to  observe  the  total  eclipse  of  the 
Sun,  I  took  advantage  of  my  stay  at  Tunis  to  pay 


22  A   DAY   IN   THE   MOON 

a  visit  to  Pere  Delattre,  who,  as  is  well  known,  has 
with  admirable  patience  brought  together  in  a 
museum,  that  is  unique  in  the  world,  the  materials 
for  a  reconstruction  of  Carthaginian  civilisation. 

My  colleagues  and  myself  were  not  a  little  sur- 
prised at  being  shown,  amongst  other  remarkable 
objects,  a  cameo  carved  as  an  intaglio,  with  a  design 
of  singular  perfection.  It  represented  a  horse  scratch- 
ing its  head  with  its  hind  hoof.  The  minute 
details  of  the  mane  suggested  to  me  the  idea  that 
the  artist  must  have  used  a  magnifying  glass  when 
carving  it.  And  it  actually  was  with  a  plano- 
convex lens  of  rock-crystal,  found  in  a  tomb  of 
the  same  period,  that  we  were  able  to  examine  the 
cameo  in  detail.  I  have  since  learned  that  this  is 
not  the  only  instance  of  the  same  kind. 

There  is  in  the  French  Cabinet  des  Medailles  a 
seal  attributed  to  Michel  Angelo,  but  which  is 
really  of  much  earlier  date.  Fifteen  figures  are 
engraved  on  it  in  a  circle  of  a  radius  of  only 
7  millimetres.1  These  figures  are  not  all  visible 
to  the  naked  eye. 

Cicero    relates    a   still    more    extraordinary    fact. 

1  A  little  more  than  a  quarter  of  an  inch  (0*275  *"•)•  The  diameter 
would  thus  be  about  half  an  inch  (0-55  in.). 


OBSERVATIONS   OF   THE   ANCIENTS    23 

He  tells  of  an  artist  having  written  out  the  whole 
of  Homer's  Iliad  in  microscopic  characters. 

One  may  judge  of  the  minuteness  of  the  work, 
when  it  is  added  that,  according  to  the  same 
author,  the  piece  of  parchment  could  be  contained 
in  a  nutshell. 

Pliny  also  relates  that  Mymecides  had  sculptured 
in  ivory  the  representation  of  a  four-horse  chariot 
so  small  that  a  fly  could  have  covered  it  with  its 
wings. 

The  Greeks  and  Romans  must  therefore  have 
known  the  magnifying  power  of  optical  lenses. 

If  there  were  any  doubt  of  this,  we  need  only 
recall  the  story  of  that  magnifying  glass  in  the 
Carthage  Museum.  In  the  same  cases  of  the 
museum  one  can  see  similar  lenses  made  of  glass, 
but  these  have  become  opaque  with  the  lapse  of 
time. 

But  as  long  ago  as  1852  Sir  David  Brewster 
exhibited,  at  a  meeting  of  the  British  Association, 
a  lens  of  rock-crystal,  which  had  lately  been  found 
in  the  excavations  of  Nineveh. 

It  is  therefore  quite  natural  to  suppose  that  the 
ancients  might  very  well  have  reached  a  knowledge 
of  optical  instruments  such  as  microscopes  and 


24  A   DAY   IN   THE   MOON 

telescopes,  all  the  more  because  what  is  essentially 
required  for  such  instruments  is  only  the  placing 
together  of  a  couple  of  magnifying  lenses. 

There  is  all  the  more  to  be  said  for  this  theory 
because  if  we  deny  to  the  peoples  of  antiquity  this 
useful  knowledge,  it  is  impossible  to  explain  a 
good  many  statements  they  make — amongst  others, 
this  which  I  take  from  Democritus.  This  philo- 
sopher affirmed  that  the  Milky  Way  was  made  up 
of  a  countless  number  of  stars,  and  that  it  was 
the  confused  mingling  of  their  light  that  was  the 
cause  of  its  phosphorescent  whiteness.  How  could 
Democritus  have  imagined  such  an  explanation  at  a 
period  when  the  nations  of  his  time  still  believed 
in  the  legend  of  the  drops  of  milk  from  the  breasts 
of  Juno  ? 

It  may  be  that  the  ancients  even  knew  something 
of  the  reflecting  telescope,  the  instrument  made  with 
a  concave  mirror.  And  this  supposition  is  not  more 
unlikely  than  the  other. 

Some  writers  appeal  in  support  of  this  idea  to 
the  burning  mirrors  that  Archimedes  used  at  the 
siege  of  Syracuse  to  set  on  fire  the  ships  of 
Marcellus. 

But  it  seems  to  be  now  fairly  well  ascertained 


OBSERVATIONS   OF   THE   ANCIENTS    25 

that  the  mirrors  in  question  were  not  concave,  or 
of  a  single  piece,  but  formed  of  a  great  number  of 
flat  reflecting  surfaces  at  various  angles  concentrating 
the  solar  rays  on  the  same  point. 

Such  an  arrangement  can  produce  the  same 
concentration  of  heat  as  the  concave  mirror  of  a 
telescope,  and  BufFon,  by  means  of  148  plane 
mirrors,  once  succeeded  in  setting  fire  to  a  deal 
board  at  a  distance  of  49  metres  (about  160  ft.). 

Critics  have,  however,  always  been  very  reserved 
when  it  comes  to  the  question  of  explaining  a 
statement  made  by  serious  historical  writers  re- 
garding vision  by  means  of  some  unknown 
apparatus. 

Ptolemy  Euergetes,  the  brother  of  King  Ptolemy 
Philadelphus,  who  lived  in  the  third  century  before 
Christ,  had  caused  to  be  fixed  on  the  summit  of  the 
lighthouse  of  Alexandria  an  instrument  with  which 
ships  could  be  seen  at  a  great  distance.  Many 
authors  have  suggested  that  this  may  have  been  a 
concave  mirror. 

The  thing  is  quite  possible,  but  it  must  be  added 
that  a  mirror  of  this  kind  could  be  of  no  use 
whatever  for  bringing  distant  objects  near  without 
the  addition  of  a  lens.  But  there  is  no  reason 


26  A   DAY   IN   THE    MOON 

why  such  an  optical  device  should  not  have  been 
adopted  at  this  period.  This  is  shown  by  the 
evidence  already  cited. 

When  therefore  Galileo  directed  his  telescope  at 
the  Moon,  it  was  perhaps  not  the  first  time  that 
man  had  made  celestial  objects  seem  nearer  to  him, 
and  who  can  say  if  the  priests  of  old  Egypt  may 
not  have  watched  from  the  summits  of  their 
observatories  the  last  eruptions  of  the  lunar 
volcanoes  ? 


Ill 

THE    MOON   AS    SEEN    BY   THE 
NAKED    EYE 

ONE  September  day  some  years  ago  I  was  in  Paris 
taking  a  quiet  walk  along  the  quays  by  the  Seine, 
when  there  suddenly  came  to  me  the  idea  of  making 
a  long  journey.  I  had  three  weeks  in  front  of  me, 
more  than  is  necessary  for  getting  far  away  from 
the  capital. 

On  one  point  only  I  was  embarrassed.  Where 
was  I  to  go  ? 

But  two  hours  later  I  was  in  the  express  on  my 
way  to  Amsterdam.  I  had  taken  the  first  train  1 
found  starting  from  the  Gare  du  Nord. 

And  this  was  how  I  came  to  visit  Holland. 

But  I  would  not  now  advise  anyone  to  adopt 
this  way  of  setting  out  on  a  journey. 

Those  who  study  in  advance  the  regions  they 
are  about  to  visit  (and  there  are  many  who  do  so) 

seem  to  me  to  be  much  better  advised. 

27 


28  A   DAY   IN  THE   MOON 

Let  us  imitate  those  serious  and  sensible  people, 
and  before  setting  out  for  the  Moon  let  us  study 
together  the  facts  that  are  essential  for  the  under- 
standing of  the  celestial  phenomena  connected  with 
our  satellite. 

And,  first  of  all,  what  is  a  satellite  ?  What  is 
the  meaning  of  this  word  that  we  so  often  apply 
to  the  Moon  ? 

You  know  that  the  Solar  System  is  composed 
of  a  great  central  body  round  which  revolve  certain 
planets,  smaller  than  itself. 

Now,  these  planets  are  in  several  cases  accom- 
panied in  their  stately  movement  of  revolution  by 
other  stars  smaller  than  themselves,  as  a  kind  of 
bodyguard. 

The  number  with  each  planet  varies.  Mars  has 
two  of  them,  Jupiter  eight,  and  a  telescope  of  very 
moderate  power  will  show  you  the  four  largest  of 
these. 

If  we  could  go  away  some  hundreds  of  thousands 
of  miles  from  our  Earth,  we  should  see  that  it 
was,  in  the  same  way,  accompanied  in  its  rapid 
course  by  a  single  satellite.  This  only  child  of  our 
dear  mother  Earth  is  the  Moon. 

Let  us  go  back  in  imagination  several  thousand 


29 

centuries  to  the  time  when  the  Earth,  a  vast 
globular  mass  of  gas  at  a  high  temperature,  shone 
like  a  miniature  sun. 

Beside  this  relatively  small  star  there  would  be 
not  a  trace  of  a  satellite,  but  around  it  an  immense 
ring  of  diffused  matter  resembling,  though  of  more 
restricted  dimensions,  that  which  we  see  in  the 
nebula  of  the  constellation  Lyra. 

Ages  pass  by,  and  the  spectacle  has  gradually 
changed.  There  has  been  a  movement  of  the 
Earth's  axis,  and  now  all  the  material  of  its  primi- 
tive ring,  instead  of  lying  in  spirals  around  it,  has 
concentrated  into  a  single  compact  mass.  The 
ring  has  been  the  origin  of  a  very  small  luminous 
body  revolving  round  that  star — the  Earth. 

Earth  and  Moon  at  this  epoch  shone  with  a 
brightness  that  was  all  their  own.  They  formed 
in  the  heavens  one  of  the  lesser  double  stars,  of 
which  the  component  units  are  linked  together  by 
the  laws  of  attraction. 

To  analyse  what  must  have  taken  place  under 
these  new  conditions  of  existence  is  a  problem  of 
celestial  mechanics  that  is  easy  of  solution. 

First  of  all,  like  all  the  heavenly  bodies,  the 
Moon  turned  on  its  own  axis — that  is  to  say,  to 


30  A   DAY   IN  THE   MOON 

its  movement  of  revolution,  making  it  follow  an 
orbit  round  the  Earth,  there  was  added  a  movement 
of  rotation  on  itself  completed  in  the  course  of  a 
few  hours. 

But  when  two  bodies  in  a  fluid  state  are  in 
presence  of  each  other  at  a  moderate  distance,  an 
elongation  of  their  shape  is  produced,  a  kind  of 
spreading  out  in  the  direction  of  the  line  joining 
them  together  ;  it  is  the  same  phenomenon  as 
that  of  the  tides,  and  each  region  as  it  passes 
before  the  attracting  body  is  in  turn  influenced 
by  it. 

Now,  the  mass  of  the  Earth  is  enormous  in 
comparison  with  that  of  the  Moon,  and  accord- 
ingly at  this  remote  period  the  tides  of  the 
satellite  must  have  been  produced  with  extra- 
ordinary intensity. 

Thus  at  each  turn  of  its  rotation  the  convex 
distortion  of  the  lunar  mass  under  the  attraction 
of  our  globe  would  act  just  like  a  brake  applied 
to  the  Moon,  generally  retarding  its  motion,  so 
that  the  final  result  of  this  phenomenon  would  be 
that  the  time  of  its  rotation  on  its  axis  and  its 
revolution  round  the  earth  would  gradually  become 
equal. 


From  a  photograph. 


EARTH-LIT  NEW  MOON. 


30] 


AS   SEEN   BY   THE   NAKED   EYE      31 

At  present  things  go  on  just  as  if  the  Moon 
were  fixed  to  the  Earth  by  an  enormous  arm  keeping 
it  in  the  same  relative  position,  and  checking  any 
deviation  to  right  or  left. 

And  this  is  why  we  always  see  the  same  side  of 
the  Moon. 

The  ancients  had  long  ago  noticed  this  fact, 
which  you  yourself  can  test  by  observation  with 
the  naked  eye,  especially  at  the  time  of  the  Full 
Moon,  when  you  will  see  that  the  spots  are  always 
arranged  in  the  same  way. 

From  remote  times  the  peoples  of  antiquity 
traced  in  it  a  kind  of  human  face  with  two  eyes, 
a  mouth,  and  'a  nose.  Sometimes,  as  nowadays, 
men  took  the  appearance  to  be  that  of  a  man 
bending  under  a  burden. 

Albertus  Magnus  has  left  us  a  description  of 
the  Moon  which  is  extremely  precise  for  a  time 
when  the  human  eye  was  not  aided  by  magnifying 
instruments.  Well,  this  description  corresponds  very 
exactly  with  what  an  astronomer  of  to-day  would 
say. 

So  the  Moon,  since  man  appeared  on  the  Earth, 
has  always  presented  the  same  side  to  us. 

Are  we   to  conclude  from  this   that  it  does   not 


32  A   DAY    IN   THE    MOON 

rotate  upon  itself?  If  you  please,  do  not  jump 
to  hasty  conclusions,  but  let  us  examine  the  question 
more  closely. 

Walk  round  a  table  in  the  middle  of  which  you 
have  placed  something,  and  don't  take  your  eyes 
off  this  object,  which  will  represent  the  Earth, 
while  you  are  playing  the  part  of  the  Moon. 

When  you  have  gone  half-way  round,  it  is 
evident  that  you  will  be  facing  the  wall  of  the 
room  that  was  behind  you  at  the  beginning  of 
the  experiment.  Thus,  without  paying  attention 
to  it,  you  will  have  already  yourself  turned  half- 
round. 

Finally,  by  the  time  you  have  come  back  to  the 
point  you  started  from,  you  will  have  completed 
one  round  "  of  your  orbit,"  and  at  the  same  time 
you  yourself  will  have  turned  completely  round, 
just  as  if  you  had  made  a  slow  pirouette  on  your  feet. 

There  would  be  just  the  same  sort  of  thing  if 
a  balloon  could  go  all  round  the  world.  When 
they  reached  the  Antipodes  the  aeronauts,  compared 
with  ourselves  in  the  north,  would  be  head  down- 
wards, and  by  the  time  they  returned  to  our  regions 
they  would  have  slowly  made  a  regular  somersault, 
like  the  clowns  in  a  circus. 


AS  SEEN   BY   THE   NAKED   EYE      33 

And  nevertheless  during  all  this  voyage  men 
remaining  below  on  the  Earth  would  see  only  the 
lower  part  of  the  balloon,  which  would  always  keep 
the  same  side  towards  them,  just  as  the  moon  does. 

"  Well,  then,"  you  will  say,  "  we  are  condemned 
never  to  have  a  sight  of  the  other  hemisphere  of 
the  Moon  ?  " 

"  Evidently." 

"  Has  it  the  same  structure  as  that  which  we 
can  see — craters,  mountains,  valleys,  etc.  ?  " 

This  is  a  point  to  which  we  shall  return  later  on. 

The  other  side  of  the  Moon,  precisely  because  we 
cannot  see  it,  and  shall  never  see  it — at  least  unless 
we  go  there — has  always,  like  all  unknown  things, 
exercised  a  mysterious  attraction  on  selenographers, 
and  we  shall  refer  to  it  again. 

Let  us  come  back,  then,  to  the  subject  of  the 
appearance  of  the  Moon. 

I  have  met  many  persons  who  do  not  even 
yet  understand  why  the  Moon  does  not  always 
appear  under  the  form  of  a  perfectly  circular  disc. 
They  have  remained  in  the  same  state  of  knowledge 
as  was  that  of  remote  antiquity,  or  rather  they 
have  no  ideas  on  the  subject.  They  don't  know, 
and  they  are  not  anxious  to  know. 
3 


34  A   DAY    IN    THE    MOON 

The  Chaldasan  astronomer  Berosus,  to  explain 
the  phenomenon,  supposed  that  the  Moon  was  a 
globe  half  alight  and  half  dark,  and  that  in  turning 
upon  its  axis  it  showed  us  these  different  regions 
in  succession. 

However,  there  were,  even  before  Berosus, 
philosophers  who  knew  better,  and  had  found 
out  the  true  explanation. 

Thales  had  perfectly  well  noted  that  the  Moon 
received  its  light  from  the  Sun,  and  later  Aristarchus 
rightly  remarked  that  at  the  moment  when  the 
Moon  was  half  lighted  up,  the  Earth  was  exactly 
opposite  the  dividing  line  between  light  and 
darkness,  while  the  direction  of  the  Sun  was  at 
right  angles  with  the  line  between  Earth  and  Moon. 

Make  the  experiment  yourself  with  a  white 
ball  hanging  by  a  string  in  a  room  lighted  by  a 
single  lamp,  and  you  will  soon  succeed  in  working 
out  the  position  of  which  Aristarchus  speaks. 

This  able  mathematician  did  even  better.  From 
this  observation  he  deduced  a  method  of  measuring 
the  distance  of  the  Sun,  and  he  found  that  it  was 
nineteen  times  greater  than  the  space  that  separates 
us  from  the  Moon. 

He   had   made   a   mistake  in   the   application  of 


Photograph  by  the  Lick  Observatory. 

THE  MOON  AT  THE  FIRST  QUARTER 

(Aged  7  days  3  hours). 


34] 


AS   SEEN   BY   THE   NAKED   EYE      35 

his  idea,  but  in  principle  it  was  right  enough,  and 
Kepler  more  than  once  recommended  this  method. 

Vendelinus  and  Riccioli  made  use  of  it,  but  with- 
out any  more  success.  In  a  telescope  the  Moon 
in  fact  does  not  appear  as  a  perfectly  even  sphere, 
and  the  irregularities  of  its  surface  make  it  hopeless 
to  fix  any  precise  moment  when  the  line  between 
light  and  shadow  is  really  a  straight  one. 

But,  on  the  other  hand,  the  invention  of  the 
telescope  in  1610  removed  all  possible  doubt  as 
to  the  explanation  of  the  Moon's  phases. 

In  the  field  of  view  of  the  instrument  it  was 
in  fact  easy  to  follow  hour  by  hour  the  flooding  of 
new  regions  of  the  Moon  by  the  Sun's  light. 

And,  nevertheless,  though  one  can  hardly 
believe  it,  in  1613  Albergotti  still  taught,  as  a 
professor  of  Astronomy,  that  the  Moon  gave  a  light 
of  its  own,  and  to  prove  this  he  appealed  to 
Biblical  texts  which  he  interpreted  in  his  own  way. 
This  mania  for  mixing,  without  any  reason,  Holy 
Scripture  and  scientific  theory  (from  which,  by  the 
way,  Galileo  himself  was  not  exempt)  seems  to  us 
nowadays  extraordinary.  And,  nevertheless,  I  have 
come  across  it  more  than  once,  as  is  shown  by 
many  letters  I  have  received  on  the  subject. 


36  A   DAY   IN  THE   MOON 

A  little  reflection,  seasoned  with  some  extremely 
simple  experiments,  will  show  us  the  real  mechanism 
of  the  phases  of  the  Moon. 

Let  us  take  once  more  our  white  ball,  hanging 
on  a  string  and  held  at  arm's  length,  with  a  lamp 
placed  on  a  table  on  a  level  with  the  eye,  and, 
without  moving  from  the  spot  where  you  stand, 
carry  the  ball  in  a  circle  round  your  head,  which 
will  represent  the  Earth. 

Only  you  must  take  care  to  keep  the  ball  a 
little  above  the  level  of  the  eye,  for  the  Moon 
moves  in  an  orbit  slightly  inclined  to  the  path 
followed  by  the  Earth. 

Let  us  begin  with  the  position  of  Full  Moon. 

The  ball  is  at  the  other  side  of  your  head  from 
the  lamp.  Facing  it,  you  see  that  it  presents  a 
disc  entirely  illuminated. 

As  you  move  it  from  this  position  you  begin  to 
perceive  a  narrow  segment  of  shadow,  cutting  ofF 
a  little  of  the  illuminated  circle.  As  you  continue 
the  movement  in  the  same  direction  you  arrive  at 
the  Last  Quarter,  and  the  boundary  line  between 
the  shadow  and  the  light  will  divide  the  disc  into 
two  equal  parts,  the  lighted  part  being  to  the  left. 

Again  a  slight  movement,  and  the  shadow  will 


Direction,  of     Sun, 


Full  Z  Moon 


THE  PHASES  OF  THE  MOON. 


361 


AS   SEEN   BY   THE   NAKED   EYE      37 

gain  further  ground,  and  soon  leave  only  quite  a 
thin  crescent.  As  soon  as  the  Moon  is  in  the  same 
direction  as  the  Sun,  above  or  below  it,  it  turns  its 
dark  side  to  us  and  the  disc  entirely  disappears. 
This  is  the  Old  Moon. 

Starting  from  this  position  we  have  the  phases  in 
reversed  order,  and  we  come  to  the  First  Quarter, 
and  then  the  Full  Moon,  and  so  on. 

If  the  experiment  is  reversed,  going  round  the 
ball  held  at  arm's  length  so  that  your  head  re- 
presents the  Moon,  you  will  see  that  our  Earth 
would  present  to  the  Selenites1 — as  we  might  call 
the  inhabitants  of  the  Moon,  if  there  were  any — 
similar  phases,  but  in  the  opposite  order. 

In  other  words,  when,  for  instance,  after  the  New 
Moon  the  people  of  the  Earth  see  their  satellite 
under  the  form  of  a  crescent,  the  Selenites  would 
see  the  Earth  in  its  last  quarter,  that  is  to  say 
three-fourths  illuminated. 

And  this  remark  will  explain  to  you  why  at  this 
period  of  the  lunar  month  we  see  not  only  a  thin 
and  very  bright  crescent,  but  sometimes  the  rest  of 
the  Moon  dimly  illuminated  by  the  diffused  reflec- 
tion from  the  Earth. 

From  Selene,  the  Greek  name  for  the  Moon. — Translator's  Note. 


38  A   DAY    IN   THE    MOON 

This  is  what  is  called  the  "  earth-shine  "  on  the 
Moon. 

We  have  said  that  the  Moon  revolves  in  an 
orbit  obliquely  inclined  to  the  plane  of  our  own. 
The  inclination  is  slight — only  5°  8' — but  it  is 
nearly  constant.  The  result  is  that  the  Moon  does 
not  always  pass  precisely  between  us  and  the  Sun. 
If  it  passes  at  a  point  where  it  hides  that  brilliant 
disc  from  us,  there  is  an  eclipse  of  the  Sun.  If,  on 
the  other  hand,  when  passing  on  the  opposite  side  of 
the  Earth,  it  is  hidden  in  the  shadow  of  our  planet, 
there  is  an  eclipse  of  the  Moon. 

These  two  phenomena  therefore  take  place  only 
at  the  time  of  New  or  Full  Moon,  and  they  recur 
in  a  series  that  extends  over  about  eighteen  years. 

These  are  extremely  interesting  topics  from  the 
astronomical  point  of  view,  and  we  shall  return  to 
them.  But  we  shall  end  this  chapter  with  an 
attempt  to  solve  a  question  which  has  caused  the 
expenditure  of  floods  of  ink  since  first  men  became 
interested  in  it. 

Why  does  the  Moon  appear  larger  on  the  horizon 
than  when  at  its  highest  point  ? 

I  have  said  "  appear  larger,"  because  this  is  cer- 
tainly a  mere  optical  illusion. 


Photograph  by  P.  Puiseuz,  Paris. 

THE   MOON 
(Aged  8  days  23$  hours.    February  6th,  1903,  4.3  a.m.). 


38] 


AS   SEEN   BY   THE   NAKED   EYE      39 

In  reality  its  disc  is  larger  when  in  the  zenith, 
the  highest  point  of  the  sky,  than  it  is  near  the 
horizon,  as  is  shown  by  measurements  made  with  a 
micrometer  fitted  to  a  telescope.  And  this  is  what 
theory  should  lead  us  to  expect,  for  the  Moon  in 
the  zenith  is  slightly  nearer  the  observer.  But  this 
very  small  difference  is  quite  unappreciable  to  the 
naked  eye,  and  we  may  say,  still  keeping  close  to 
the  exact  truth,  that  as  seen  by  us  the  Moon  always 
occupies  precisely  the  same  amount  of  space  in  the 
heavens. 

Then  why  does  it  seem  to  us  larger  when  it  is 
near  the  horizon,  and  apparently  therefore  near  the 
Earth  ? 

And  remember  that  this  phenomenon  is  not 
something  special  to  the  Moon.  The  Sun  in  the 
same  position  also  appears  larger  to  us,  and  finally 
the  constellations  themselves  seem  to  occupy  more 
space  when  they  are  to  all  appearance  nearer  the 
ground.  The  most  humble  student  of  the  heavens 
can  see  this  for  himself  any  evening  if  he  will 
observe  the  Great  Bear  at  different  hours  of  the  night. 

There  are  plenty  of  theories  to  explain  such 
appearances.  One  of  them  is  based  on  the  fact 
that  we  cannot  avoid  mistakes  in  judging  distances 


40  A   DAY   IN   THE    MOON 

accordingly  as  the  background,  on  which  the  object 
is  seen,  is  bright  or  dark.  And  a  fog  makes 
objects  seem  larger  because  it  makes  them  seem 
farther  off.  Here  is  an  instance  of  such  a  mistake 
from  my  own  personal  experience. 

One  summer  day  about  dawn  I  was  taking  a 
walk  with  a  friend  in  a  country  that  neither  of  us 
knew  well.  The  road  rose  steeply  in  front  of  us, 
and  where  its  highest  point  met  the  sky-line  we 
saw,  coming  into  sight  over  the  crest,  what  looked 
like  someone  in  a  rather  short  dress,  such  as  the 
countrywomen  wear  in  many  parts  of  the  province 
of  Berry.  We  were  for  a  moment  in  doubt  as  to 
what  kind  of  person  we  were  about  to  meet.  I  bet 
that  it  was  an  ecclesiastic  in  a  soutane,  my  friend 
that  it  was  a  peasant  woman.  But  the  distance 
between  us  and  the  subject  of  our  wager  was  not 
at  all  as  great  as  we  imagined.  We  were  soon  close 
up  to  the  "  person "  in  question.  We  had  both 
lost  our  wager.  For  a  goose  was  walking  in  stately 
fashion  down  the  middle  of  the  road,  with  its  head 
directly  towards  us.  The  twilight  haze  had  de- 
ceived us  as  to  the  real  distance,  and  the  object, 
projected  against  what  we  thought  to  be  a  far-off 
background,  had  assumed  an  enormous  size. 


From  a  photograph. 


THE  FULL  MOON. 
(Aged  14  days  i  hour). 


40] 


AS   SEEN   BY   THE   NAKED   EYE      41 

It  is  true  that  at  the  moment  when  one  of  the 
heavenly  bodies  is  rising  its  rays  reach  us  after 
traversing  a  denser  layer  of  the  atmosphere  than 
when  it  is  nearer  the  zenith  ;  its  brightness  is 
diminished  and  it  appears  larger  to  us.  But  this  is 
only  an  imperfect  solution  of  the  problem.  For, 
as  a  matter  of  fact,  when  the  bright  disc  shows  dull 
and  grey  through  a  dense  fog  it  never  gives  us  the 
same  impression  of  size  as  the  broad  sunset  Sun. 
Fog  and  haze,  therefore,  do  not  explain  every- 
thing. 

Another  theory  is  based  on  the  absence  of  points 
of  comparison,  when  the  Sun  or  Moon  are  at  the 
highest  points  of  their  course. 

As  it  rises,  the  Moon  is  seen  as  a  part  of  the 
landscape,  and  we  have  objects  close  by  with  which 
to  compare  it.  There  are  none  of  these  as  it 
approaches  the  zenith.  It  seems  to  be  nearer  us, 
and  though  its  apparent  diameter  has  not  really 
changed,  we  think  it  looks  smaller. 

But  here  again  we  have  not  the  real  key  to  the 
riddle.  For  at  sea  in  calm  weather,  especially  in 
the  evening,  though  there  are  absolutely  no  objects 
with  which  to  compare  the  size  of  the  setting  Sun, 
the  illusion  remains  just  as  strong.  It  is  the  same 


42  A   DAY   IN   THE    MOON 

on  a  plain,  where  there  is  not  a  tree  or  a  house  to 
help  the  observer's  estimate. 

We  must  therefore,  as  I  have  shown  long  before 
this,  have  recourse  to  a  theory  based  on  psycho- 
logical principles,  and  my  explanation  rests  upon 
two  optical  illusions  that  it  is  easy  to  test. 

In  the  first  place,  the  firmament — that  is  to  say, 
the  ideal  vault  to  which,  whether  we  will  or  not,  we 
attach  in  imagination  all  the  stars,  as  if  they  were 
equally  distant — seems  to  us  a  flattened  curve  and 
not  spherical. 

The  reason  is  very  simple.  For  us  the  Earth 
seems  always  flat,  though  we  well  know  the  con- 
trary, and  the  masses  of  cloud  carried  overhead  by 
the  wind  appear  some  hours  later  to  touch  the 
horizon. 

Now,  above  the  clouds  we  place  the  stars,  and 
we  instinctively  imagine  the  vault  of  the  clouds 
and  the  stellar  vault  as  parallel  curves,  and  thus 
both  are  for  us  flattened  arches  bending  down  to 
the  horizon,  so  that  there  the  heavenly  bodies  would 
be  farther  off  than  at  the  zenith. 

If  I  am  met  with  the  objection  that  even  with 
a  clear  sky  there  is  the  impression  of  the  vault  of 
the  heavens  being  flattened  in  the  same  way,  I  find 


Photograph  by  P.  Puiseux,  Paris. 

THE    MOON 
(Aged  20  days  19  hours.    September  izth,  1903,  3.13  a.m.). 


42] 


AS  SEEN   BY  THE   NAKED   EYE      43 

an  explanation  in  the  fact  that  we  have  no  means 
of  estimating  distance  in  the  sky,  and,  whatever  be 
the  explanation  accepted,  the  error  and  illusion 
persist.  The  arch  appears  to  us  flattened  at  its 
upper  part. 

In  the  second  place,  it  is  undeniable  that  the 
apparent  dimensions  of  an  object  are  greater  when 
we  project  it  upon  a  more  distant  background. 

Do  you  want  an  example  ?  In  the  evening  look 
fixedly  at  the  incandescent  filament  of  an  electric 
light  close  to  you.  Then  suddenly  cast  your  eyes 
on  a  more  distant  object,  the  front  of  the  opposite 
house  seen  through  the  window,  or  something  still 
farther  off".  The  image  of  the  lamp,  still  seen  by 
your  eye,  will  seem  enormous,  and  will  occupy  a 
considerable  surface  of  the  dark  background. 

Here  is  the  whole  solution  of  the  problem,  and 
I  sum  it  up  in  a  single  phrase  :  the  Moon  seems 
to  us  larger  on  the  horizon  simply  on  account  of 
the  apparently  flattened  or  elliptic  form  of  the 
sky. 

Since  I  first  stated  this  theory  some  astronomers 
have  sought  for  other  explanations,  and  I  have 
found  a  better  proof  of  my  hypothesis. 

When  the  Sun  is  setting  in  a  clear  sky  and  your 


44  A   DAY    IN   THE    MOON 

eyes  can  easily  endure  its  brightness,  fix  them  for 
a  few  moments  on  its  still  brilliant  orb,  then  look 
at  another  point  of  the  horizon.  Your  retina  will 
present  to  you  a  dark  spot,  green,  bluish,  or  black, 
and  you  will  be  able  to  keep  sight  of  it  if  you 
take  care  frequently  to  wink  your  eyes. 

Note  attentively  the  apparent  size  of  this  sub- 
jective image.  It  will  naturally  appear  to  you  of 
the  same  size  as  the  solar  disc,  but — and  here  we 
have  a  complete  confirmation  of  my  theory — if  at 
this  moment  you  turn  your  gaze  towards  higher 
and  higher  points  of  the  sky,  the  same  image  will 
appear  to  be  diminished  in  size,  and  it  will  reach  its 
minimum  surface  when  you  see  it  at  the  zenith. 

Here  we  have  the  solution  of  all  difficulties,  and 
we  may  conclude  with  a  somewhat  picturesque 
passage  from  the  letters  of  Euler  to  a  German 
Princess  : 

"  I  believe,"  he  said,  with  reference  to  the  subject 
that  has  occupied  us,  "  that  I  have  placed  in  its 
true  light  the  difficulty  with  which  we  have  had 
to  deal  in  this  matter,  so  as  to  make  your  Highness 
the  better  appreciate  the  importance  of  the  true 
solution  of  this  great  problem." 


Photograph  by  the  Lick  Observatory. 

THE  MOON  AT  THE  LAST  QUARTER 

(Aged  23  days  8  hours). 


44] 


IV 
WITH   THE  EYE  AT  THE   TELESCOPE 

HERE  we  are  at  our  fourth  chat  about  "  lunar 
matters,"  and  we  have  already  made  serious  progress 
in  the  study  of  our  satellite,  from  the  mechanical 
point  of  view. 

Let  us  sum  up  rapidly  what  we  have  learned  ; 
this  will  help  us  not  to  forget,  and  give  us  the 
opportunity  of  adding  something  to  it. 

At  the  outset  the  materials  which  were  later  on 
to  form  the  Moon  were  distributed  in  the  shape 
of  an  immense  ring  encircling  the  Earth  at  a 
distance.  The  Moon  was  therefore  never  a  part 
of  the  Earth  as  the  celebrated  Laplace  believed, 
and  as  is  held  by  a  good  number  of  his  still  living 
followers. 

We  have  even  better  reason  for  not  falling  into 
the  exaggerations  of  that  American  philosopher 

who,    in    good    faith,    supposed    that    the    Moon 

45 


46  A   DAY   IN    THE    MOON 

detached  itself  one  fine  day  from  the  Earth,  at 
a  period  when  the  latter  was  already  completely 
formed. 

"This  enormous  sphere  rolling  in  space  and 
illuminating  the  landscapes  of  our  Earth,  what  is 
it  in  reality,"  he  said  recently,  "  but  a  fragment  of 
our  planet,  that  once  filled  the  gap  left  on  our 
maps  by  the  great  depression  of  the  Pacific  ? " 

Astronomy,  being  now  really  a  science,  cannot 
give  its  support  to  such  fantastic  theories. 

When  the  ring,  of  which  we  have  just  traced 
the  history,  had  concentrated  into  a  single  mass  to 
form  the  Moon,  the  latter  continued  to  revolve 
around  us,  and  Newton  was  the  first  to  show  that 
in  so  doing  it  simply  obeys  the  laws  of  gravitation. 
It  is  only  in  virtue  of  its  first  impulsive  force  that 
it  does  not  fall  directly  towards  the  Earth.  But 
let  us  suppose  that  force  suddenly  vanishes  ;  im- 
mediately the  light  of  our  nights  would,  just  like 
a  mere  stone,  begin  to  move  towards  our  globe, 
and  would  reach  it  in  less  than  five  days  of  twenty- 
four  hours. 

We  have,  for  the  sake  of  greater  simplicity, 
assumed  that  the  Moon  goes  round  us  in  a  circle. 
In  reality,  obeying  the  laws  of  motion  discovered 


WITH  THE  EYE  AT  THE  TELESCOPE   47 

by  Kepler,  her  orbit  is  slightly  flattened  in  the  form 
of  an  ellipse. 

And  the  Earth  not  being  situated  in  the  centre 
of  a  circular  orbit,  it  follows  that  the  Moon  is  now 
a  little  nearer,  now  a  little  farther  off. 

At  its  mean  distance  it  is  only  238,833  miles 
distant.  Its  movement  round  the  Earth  is  at  the 
rate  of  a  little  more  than  a  thousand  yards  a  second,1 
but  at  the  same  time  it  shares  in  the  movement  of 
our  globe  round  the  Sun. 

The  figure  which  it  describes  in  space  is  not  then 
in  reality  a  circle,  or  even  an  ellipse,  but  a  curve 
that  it  is  easier  to  represent  than  to  define. 

The  perturbations  in  our  own  movement,  which 
are  caused  by  this  ball  of  2, 1 60  miles  in  diameter, 
are  beyond  imagination. 

At  the  time  of  Full  Moon  it  diminishes  the 
attraction  of  the  Sun  ;  about  New  Moon,  when  it 
is  passing  between  us  and  the  Sun,  its  attraction 
unites  with  that  of  the  latter  in  very  slightly  altering 
the  shape  of  the  Earth's  orbit.  If  the  Moon  is 
behind  the  Earth  in  its  path  through  space,  it 
diminishes  our  velocity,  whilst  it  accelerates  it  as 
it  passes  it  front  of  us. 
1  The  average  velocity  is  3,334  ft.  per  second.— Translates  Note. 


48  A  DAY   IN  THE   MOON 

All  this  might  very  easily  be  reduced  to  calcula- 
tion, but,  alas  !  its  orbit  does  not  lie  in  the  same 
plane  as  ours,  and  we  have  seen  that  the  mean 
angle  between  the  two  planes  is  5°  8',  and  our 
having  to  speak  of  a  "  mean "  inclination  tells  us 
that  this  also  varies,  so  that  altogether  astronomers 
have  no  easy  task  in  making  their  way  through 
this  labyrinth  of  masses,  positions,  distances,  and 
the  rest. 

Add  to  this  that  the  ideal  ellipse  traced  out  by 
the  course  of  the  Moon  is  itself  deformed  by  the 
attraction  of  the  Earth  ;  that  the  flattening  of  its 
curve  becomes  more  marked  for  a  certain  time,  and 
then  again  diminishes,  and  you  have  a  feeble  idea 
of  the  Chinese  puzzle  the  Moon  inflicts  on  students 
of  the  mechanism  of  the  heavens. 

The  period  of  its  revolution — that  is  to  say,  the 
time  it  takes  to  come  back  to  the  same  apparent 
point  among  the  stars — is  known  to  the  hundredth 
of  a  second,  but  it  also  is  variable. 

Actually  it  is  about  27  days,  7  hours,  43  minutes, 
1 1 '5 5  seconds. 

During  this  time  it  appears  to  make  a  complete 
circuit  of  the  heavens  ;  it  changes  its  place  therefore 
each  day  to  a  very  perceptible  extent. 


w 

H 

•4      . 
<   X 


3 


o  oo 


WITH  THE  EYE  AT  THE  TELESCOPE   49 

And,  in  fact,  if  on  a  fine  night  you  note  the 
apparent  distance  from  the  Moon  to  a  star  in  its 
neighbourhood,  you  will  see  that  at  the  end  of  a 
few  hours  there  has  been  a  considerable  change 
of  place.  It  amounts  to  a  little  more  than 
13°  in  the  twenty-four  hours,  and  this  in  the 
contrary  direction  to  the  movement  of  the  celestial 
sphere. 

It  follows  from  this  that  each  evening  the  Moon 
is  about  three-quarters  of  an  hour  behind  its  place 
of  the  evening  before. 

The  solar  day  being  itself  a  little  variable,  one 
can  understand  that  it  is  impossible  to  base  our 
calendar  on  the  observation  of  the  Moon. 

We  shall  have  occasion  later  on  to  return  to 
some  other  points  bearing  on  this  matter,  in  order 
to  complete  our  account  of  the  movements  of  the 
Moon.  For  the  moment  we  have  something  better 
to  do.  Do  you  see  from  the  window  the  Full 
Moon  rising  slowly  in  the  sky  ? 

Let  us  go  quickly  up  to  our  observatory. 

The   night    is   perfectly  clear.     The   breeze    ha 
fallen  to  a  calm,  and  if  there  is  no  disturbance  in 
the  upper  regions  of  the  atmosphere  the  sight  to 
be  seen  with  the  telescope  will  be  wonderful. 
4 


50  A   DAY   IN   THE    MOON 

However,  we  must  not  be  in  a  hurry,  but  go  to 
work  in  a  systematic  way. 

Take  first  this  opera-glass,  which  has  a  magni- 
fying power  of  only  three  times. 

Look  through  it  ;  according  to  what  we  have 
already  said,  the  disc  of  the  Moon  ought  to  appear 
to  you  to  have  a  surface  nine  times  greater  than 
when  seen  with  the  naked  eye.  You  see  precisely 
what  Galileo  saw  the  first  time  he  directed  a 
telescope  of  this  same  power  towards  the  Moon — 
that  is  to  say,  "  precisely  the  same  "  so  far  as  size 
goes,  for  in  the  year  1610  he  did  not  first  observe 
the  Full  Moon,  but  one  of  its  phases. 

At  that  moment  certain  details  which  now  to 
you  seem  drowned  in  the  solar  light  would  be  more 
marked,  and  so  it  was  he  compared  them  to  the 
eyes  of  a  peacock's  tail,  thus  linking  the  graces  of 
Diana  and  the  charms  of  Juno's  bird. 

But  what  you  can  now  see  much  more  plainly  than 
with  the  naked  eye  are  the  dark,  irregularly  dis- 
tributed spots. 

You  no  longer  recognise  the  face  you  have  been 
used  to  find  there,  and  which  the  ancients  saw  there 
more  than  two  thousand  years  ago,  as  is  proved  by 
these  verses  of  Amyot,  a  translation  from  the  Greek 


.. 

s\1  '  '     J* 

Oesenianhit  rt  am  en  j 
et 


DE  RHEITA'S  MAP  OF  THE  MOON, 
A.D.  1645. 


WITH  THE  EYE  AT  THE  TELESCOPE   53 

of    Plutarch,   who   himself  was   quoting   the   poet 
Agesianax  : — 

"De  feu  luisant  elle  est  environnee 
Tout  a  1'entour;  la  face  enlumin£e 
D'une  pucelle  apparaist  au  milieu, 
De  qui  1'oeil  semble  etre  plus  rouge  que  bleu, 
La  joue  un  peu  du  rouge  coloree."  * 

All  these  sombre  surfaces  were  a  great  puzzle  to 
the  old  astronomers,  who  at  last  took  them  to  be 
vast  seas. 

After  all,  it  was  not  such  a  bad  guess,  and  Pere 
de  Rheita  gives  us  an  explanation  of  it  in  a  book 
he  published  at  Antwerp  in  1645. 

11  Not  only,"  he  says,  c<  the  aspect  of  the  Full 
Moon  is  not  different  from  that  which  the  Earth 
presents  when  seen  in  very  fine  weather  from  the 
top  of  a  high  mountain,  but  it  greatly  resembles 
it.  In  fact,  as  one  has  often  been  able  to  verify 
by  actual  experience,  the  meadows  and  fields,  the 
mountains  and  the  valleys,  illuminated  by  the  light 
of  the  sun  and  bathed  in  it,  are  plainly  visible 
from  the  summit  of  a  mountain,  while  the  waters, 
the  lakes,  rivers,  and  seas  really  look  darker. 

"  She  is  environed  all  round  with  gleaming  fire ;  in  the  midst 
appears  the  illumined  face  of  a  maiden,  whose  eye  seems  to  be  red 
rather  than  blue,  and  her  cheek  slightly  tinted  with  red." 


54  A   DAY   IN   THE    MOON 

"  But  if  one  were  raised  above  the  Earth  a 
thousand,  ten  thousand,  or  twenty  thousand  leagues, 
or  the  whole  distance  that  separates  us  from  the 
Moon,  and  if  one  then  observed  the  Earth  with 
an  excellent  telescope,  I  have  no  doubt  that  it 
would  appear  to  present  a  great  resemblance  to  the 
face  of  the  Moon." 

It  was  therefore  admitted  at  this  period  that  the 
dark  spots  were  seas,  to  which  names  were  given  ; 
and  although  it  is  now  proved  that  the  Moon  does 
not  contain  a  single  drop  of  water,  astronomers 
have  been  so  lazy,  as  to  make  no  practical  protest 
against  this  deplorable  system  of  names. 

Kepler  and  Scheiner  indeed  made  maps  of  our 
satellite,  but  the  first  map  worthy  of  the  name  was 
engraved  by  Michael  Florentins  van  Langren, 
generally  known  by  the  name  of  Langrenus.  This 
map  was  completed  and  published  in  1645. 

Its  author  was  probably  the  first  to  apply  the 
names  of  celebrated  men  to  the  features  of  the 
Moon. 

At  the  same  time  Peyresc  and  Canon  Gassendi 
of  Digne  also  set  to  work  on  a  complete  map, 
but  they  abandoned  their  task  when  they  heard 
that  Hevelius  had  the  same  idea. 


WITH  THE  EYE  AT  THE  TELESCOPE   55 

But  put  away  your  opera-glass,  and  be  so  good 
as  to  look  through  this  telescope  of  moderate 
power,  which  magnifies  thirty  diameters.  The 
fresh  details  you  can  now  make  out  will  give  you 
an  idea  of  the  complex  spectacle  the  disc  of  the 
Full  Moon  presented  to  the  astronomers  of  1650, 
when  they  made  up  their  minds  to  set  it  down 
in  a  drawing. 

The  lunar  mountains  appearing  in  brilliant  light  ; 
certain  craters  and  circles  showing  their  darker 
interior  ;  whitish  streaks  radiating  from  the  sides  of 
some  of  them  ;  and  the  greyish  surface  of  the 
"  seas  " — which  are  nothing  of  the  kind — all  to- 
gether present  a  variety  of  aspects  that  is  somewhat 
confusing. 

One  would  think  it  would  have  opened  the 
eyes  of  the  first  selenographers  to  the  real  facts 
of  the  case. 

Not  at  all.  Hevelius  did  like  his  predecessors 
and  even  exaggerated  their  nomenclature. 

This  Hevelius,  whose  real  name  was  Hovel,  was 
a  most  enthusiastic  student  of  the  Moon. 

He  was  born  at  Dantzig  in  1 6 1 1 .  His  father, 
a  rich  brewer  in  that  city,  intended  him  for 
business,  but  Hevelius  had  other  plans.  When 


56  A   DAY   IN   THE    MOON 

still  young,  he  set  off  to  London  to  complete  his 
studies,  and  then  he  went  to  Paris,  where  he  formed 
a  friendship  with  Pere  Mersenne,  Boulliaud,  and 
Gassendi,  then  a  professor  at  the  College  de  France. 

Till  then  he  had  been  specially  devoted  to 
mathematics,  but  an  eclipse  of  the  Sun,  which 
'took  place  on  June  i,  1631,  keenly  interested 
him  in  Astronomy. 

Returning  to  his  native  city  in  1634,  he  succeeded 
to  the  brewery,  but  his  one  real  interest  was  the 
study  of  the  Moon.  The  observations  which  he 
made  at  night  he  himself  engraved  on  copper 
next  day. 

He  thus  obtained  plates  of  singular  beauty, 
which  for  more  than  a  century  were  recognised 
as  authoritative  in  the  world  of  selenography. 

When  it  came  to  giving  names  to  the  points 
shown  on  his  chart  he  found  himself  in  a  difficulty. 

He  would  have  liked  to  place  "  up  there  "  the 
names  of  famous  men,  but,  as  he  himself  tells  us, 
he  abandoned  the  idea,  for  fear  of  making  enemies 
of  those  who  were  left  out,  or  who  might  think 
their  share  too  small. 

He  therefore  decided  to  transfer  to  the  Moon 
the  names  of  our  seas,  cities,  and  mountains. 


WITH  THE  EYE  AT  THE  TELESCOPE   57 

But  of  all  this  system  of  names,  which  was  just 
as  good  as  any  other,  and  which  was  published  after 
five  years  of  arduous  observation  in  his  Seleno- 
graphia,  there  remain  now  on  our  lunar  maps 
out  of  250  names  only  those  of  the  Alps,  the 
Apennines,  and  of  four  "  promontories." 

The  Jesuit  Riccioli  of  Bologna  had  not  the 
same  fears  as  Hevelius. 

He  knew  men,  and,  making  use  of  the  obser- 
vations of  his  colleague  Grimaldi,  he  did  not 
hesitate  to  place  the  names  of  learned  men  on  the 
map  of  the  Moon. 

These,  flattered  in  their  self-love,  were  sure  to 
buy  copies,  and  this  is  how  since  1651  the  Moon 
has  become  the  "  cemetery  of  astronomers "  and 
the  "  Pantheon  of  savants." 

It  is  true  that  certain  discontented  spirits  made 
some  small  protests,  and  accused  Riccioli  of  having 
given  more  than  their  due  share  to  his  illustrious 
colleagues  of  the  Society  of  Jesus  ;  but  the  fear  of 
being  struck  out  of  the  list  carried  the  day,  and 
everyone  was  satisfied. 

Besides,  the  learned  of  earlier  days  were  not 
forgotten,  and  there  were  seen  rising  above  the 
surface  of  the  Moon  famous  craters  and  mountain- 


58  A   DAY   IN   THE    MOON 

walled  plains  bearing  the  names  of  Archimedes, 
Plato,  Aristarchus,  Ptolemy,  Copernicus,  Tycho, 
Kepler,  and  the  rest. 

The  names  of  the  seas  adopted  by  Hevelius,  the 
Caspian,  the  Mediterranean,  the  Euxine,  etc.,  were 
replaced  by  such  names  as  the  Sea  of  Storms,  the 
Sea  of  Humours,  of  Rains,  of  Fecundity,  of  Cold, 
and  other  equally  fanciful  titles. 

We  must  go  on  to  1680  before  we  find  another 
interesting  attempt  to  produce  a  map  of  the  Moon. 
The  Italian  Domenico  Cassini  had  received  letters 
of  naturalisation  in  France,  and  was  the  first 
director  of  the  Observatory  of  Paris.  Beginning 
in  1673,  he  arranged  for  drawings  of  the  phases 
of  the  Moon  to  be  made  day  after  day  by  Patigny. 
For  this  work  the  artist  made  use  of  a  large  34-feet 
telescope,  which  still  exists. 

The  drawings  were  not  published,  but  Cassini 
prepared  from  them  a  map,  including  also  his 
own  observations.  It  appeared  in  1692,  and 
the  copper-plate  was  long  kept  at  the  Royal 
Printing  Office  ;  but  one  fine  day  the  director  of 
this  State  institution  thought  it  was  time  to 
get  rid  of  some  of  the  material  that  was  piled 
up  in  his  storehouses,  and  the  map  of  Cassini 


Facsimile  of  an  engraving  in  the  "  Machina  Ccelestis." 

HEVELIUS  AND  HIS  WIFE  OBSERVING  THE  POSITIONS  OF  THE 
HEAVENLY  BODIES. 

58] 


WITH  THE  EYE  AT  THE  TELESCOPE   59 

was  included  in   a  lot  of  copper-plates   sold   to   a 
boiler-maker. 

And  it  was  a  great  pity,  for  though  we  still 
possess  some  reduced  copies  of  this  fine  piece  of 
work,  not  one  example  of  the  original  has  come 
down  to  us. 

Arago,  who  tells  the  story,  which  he  heard  from 
Bouvard,  adds  rather  naively,  "  This  director  was 
not,  one  may  presume,  a  lover  of  Astronomy." 
We  can  well  believe  it. 

Cassini's  plate  was  rather  more  than  a  foot  and 
a  half  in  diameter.  La  Hire  soon  after  undertook 
the  production  of  a  globe  of  the  Moon,  and  then 
a  map  4  metres  in  diameter,  which  was  long  dis- 
played in  a  black  frame  on  the  staircase  of  the 
library  of  Sainte-Genevieve. 

Then  came  (1762)  the  reduced  map  of  Tobias 
Mayer  (20  centimetres  in  diameter *),  which  remained 
the  only  exact  one  till  1824. 

Sir  William  Herschel  paid  much  attention  to 
lunar  studies,  but  he  has  left  us  no  drawings  of 
his  observations.  Nevertheless,  he  indirectly  con- 
tributed to  a  deeper  knowledge  of  our  satellite, 
and  this  in  a  rather  unexpected  way. 
1  I.e.  not  quite  8  inches. 


60  A   DAY   IN   THE   MOON 

As  he  had  concave  mirrors  for  telescopes  con- 
structed by  hundreds  in  order  to  choose  the  best 
of  them  for  his  own  observations,  and  as  at  the 
same  time  the  salary  he  received  was  insufficient 
for  his  expenses,  he  had  the  idea  of  selling  to  his 
brother  astronomers  the  mirrors  he  did  not  use. 

Soon  he  had  a  European  fame  as  an  optician. 
Everywhere  his  telescopes  were  appreciated  at  their 
true  value,  and  for  once  the  proverb  which  says 
that  "  Astronomy  does  not  feed  its  adepts "  was 
found  to  be  incorrect. 

The  sale  of  his  mirrors  was  for  Herschel  a 
source  of  almost  unlimited  profit. 

The  King  of  England  ordered  from  him  four 
telescopes  of  lo-feet  focus.  Herschel  let  him  have 
them  for  ,£660 — a  mere  nothing.  The  King  of 
Spain  was  more  generous,  and  paid  him  .£3,150 
for  a  telescope  of  25-feet  focal  length.  Two  smaller 
instruments  were  bought  by  Lucien  Bonaparte  in 
1814  at  the  price  of  £2,310. 

The  regular  scale  of  prices  began  at  £228  for 
a  reflector  of  y-feet  focus,  and  went  up  to  £2,600 
for  an  instrument  of  20  feet.  The  orders  were 
numberless. 

One  might  at  first  sight  think  that  the  distribu- 


THE  MOON. 


60] 


WITH  THE  EYE  AT  THE  TELESCOPE   61 

tion  throughout  the  learned  world  of  these  powerful 
telescopes,  far  superior  to  those  that  had  been  con- 
structed before  Herschel's  time,  would  result  in 
enormous  progress  in  Astronomy. 

But  there  was  nothing  of  the  kind  ;  and  this 
once  more  proves  the  assertion  that  "  The  most 
essential  part  of  an  optical  instrument  is  the  eye 
that  looks  through  the  eye-piece." 

To  do  useful  work  in  Physical  Astronomy,  what 
is  wanted  is,  in  fact,  the  skilled  eye  guided  by  a 
brain.  Hence  the  need  of  a  long  and  patient 
training  of  the  sense  of  sight,  attentive  and  reason- 
ing observation  of  the  phenomena  to  which  it  is 
directed  ;  perfect  sincerity,  the  entire  abandonment 
of  preconceived  ideas — all  united  to  a  passionate 
love  for  science  and  truth. 

The  numerous  possessors  of  Herschel's  telescopes 
were  doubtless  lacking  in  the  required  qualities,  for 
most  of  them  made  no  new  observation  of  any 
particular  value. 

Nevertheless,  two  of  them,  Schroeter  and  Pond, 
were  exceptions,  and  thus  the  efforts  of  the  cele- 
brated Hanoverian  astronomer  in  this  direction 
were  not  useless. 

Schroeter    studied    the    Moon    for    many   years, 


62  A   DAY   IN   THE    MOON 

and    published    his    interesting    Fragmenta    Seleno- 
graphica. 

"  He  was,"  says  Goodacre,  "  a  poor  draughtsman, 
but,  notwithstanding  this  defect,  his  sketches  have 
considerable  value." 

At  the  beginning  of  the  nineteenth  century  we  find 
Lohrmann  and  Gruithuisen  at  work,  but  the  latter 
was  haunted  by  absurd  ideas  which  he  tried  to  set 
forth  in  his  drawings.  He  was  convinced  that  signs 
of  life  and  civilisation  were  to  be  seen  in  the  Moon. 

It  was  then  that  Beer  and  Madler  showed  by 
the  colossal  work  which  they  brought  to  a  successful 
completion  what  a  student  of  the  heavens  can  accom- 
plish with  the  help  of  an  instrument  of  very 
moderate  power. 

Their  telescope  had  an  aperture  of  not  quite 
4  inches  ;  and,  nevertheless,  it  was  sufficient  for 
them  to  accumulate  on  a  map  90  centimetres1  in 
diameter  such  a  number  of  details  that  the  other 
selenographers  confessed  they  had  not  the  courage 
to  compete  with  them. 

However,  in  1 8  64  the  British  Association  formed 
a  committee  with  the  chief  object  of  popularising 
the  study  of  the  Moon. 

1  35 -4  inches. 


WITH  THE  EYE  AT  THE  TELESCOPE   63 

In  1874  Nasmyth  and  Carpenter  published  a 
magnificently  illustrated  volume  representing  the 
features  of  the  Moon's  surface  from  models  made 
by  the  former  of  these  observers. 

From  the  artistic  point  of  view  no  previous 
representation  could  give  a  better  idea  of  what  one 
sees  in  the  telescope  than  those  relief-pictures  by 
Nasmyth. 

Direct  photographs  are  more  exact,  but  they  are 
far  from  having  the  charm  of  this  work,  which  one 
never  tires  of  examining. 

Neison's  book,  published  two  years  later,  pays 
special  attention  to  precision  of  detail,  and  adds 
several  thousand  new  objects. 

From  this  date  we  decidedly  enter  upon  a  new 
phase  of  Selenography.  The  work  of  Beer  and 
Madler  is  surpassed  by  these  later  productions,  to 
which  was  added  in  1878  the  largest  map  yet 
published. 

For  thirty-five  years  Schmidt  had  been  spending 
his  time  in  studying  and  drawing  the  Moon. 
Making  use  of  Lohrmann's  measurements  for  the 
positions  of  the  objects,  he  collected  together  the 
details  contained  in  more  than  three  thousand 
original  drawings,  in  a  large  map  1^87  metres  in 


64  A   DAY   IN   THE   MOON 

diameter,1  which  was  published  by  the  Prussian 
Government. 

Unfortunately,  no  second  edition  of  this  map 
was  issued,  and  it  is  now  not  to  be  had.  It  con- 
tains no  less  than  32,856  "craters." 

The  British  Association,  when  it  founded  its 
committee,  proposed  the  publication  of  a  map 
5  metres  in  diameter.2  But  this  ambitious  project 
has  not  been  carried  out. 

Though  we  have  to  do  without  this  regular 
"  ordnance  map "  of  our  satellite,  we  can  mean- 
while content  ourselves  with  the  works  of  Neison 
and  Elger,  the  drawings  of  the  French  pasteur 
Gaudibert,  and  finally  Goodacre's  map,  which 
measures  nearly  2  metres3  in  diameter.  The  author 
has  made  use  of  the  wonderful  photographs  obtained 
in  America,  and  above  all,  those  of  the  Observatory 
of  Paris,  to  fix  the  form  of  the  principal  ranges 
and  peaks,  using  special  drawings  for  the  minute 
details  that  are  only  to  be  seen  with  the  most 
powerful  instruments. 

I  suppose  you  would  like  to  see  these  fine  details 
with  your  eye  at  the  eyepiece  of  a  telescope. 

1  73-62  inches,  just  over  6  feet. 

2  A  little  over  16  feet.  z  About  6£  feet. 


WITH  THE  EYE  AT  THE  TELESCOPE   65 

But  you  should  know,  my  dear  reader,  that,  for 
this,  one  must  choose  one's  date ;  never  make 
the  experiment  at  the  time  of  Full  Moon,  but  on 
some  evening  about  the  First  Quarter,  for  instance, 
at  the  moment  when  the  Sun  is  just  lighting  up 
with  his  first  rays  the  high  summits  of  the  lunar 
Alps  and  Apennines. 

Oh !  then  I  promise  you  a  splendid  sight,  of 
which  you  can  never  tire. 

No  photograph,  no  drawing,  can  give  a  real  idea 
of  the  sight  of  the  Moon  through  a  powerful 
telescope. 

If  we  could  accomplish  this  distant  journey,  we 
should  make  it  at  one  of  these  exceptional  moments, 
so  as  to  be  able  to  watch  the  sunrise  and  see  the 
day-star  rise  slowly  in  the  sky,  lighting  up  step 
by  step  the  towering  peaks,  and  penetrating  with 
its  rays  the  hollows  of  the  yawning  craters  and  the 
black  pits  that  are  scattered  over  the  surface  of  our 
satellite,  while  its  cold  light  traces  on  the  boundless 
plains  shadows  that  stretch  away  beyond  the  reach 
of  sight. 


V 
ON   THE   WAY 

A  WEEK  has  passed  since  the  moment  when  the 
crescent  of  the  New  Moon  first  showed  itself  in  the 
twilight.  If  we  were  of  the  Mohammedan  religion 
we  would  be  careful  to  note  the  exact  hour  of  its 
appearance,  which  at  certain  periods  of  the  year 
fixes  the  end  of  the  fast  of  Ramadan. 

Some  days  after  we  noticed  the  "  earth-shine  "  on 
the  moon,  "the  Old  Moon  in  the  arms  of  the 
New,"  to  use  a  picturesque  expression  well-known 
to  astronomers.  Then,  as  the  boundary  between 
shadow  and  light  advances  little  by  little,  a  half  of 
the  disc  of  our  satellite  is  at  length  illuminating 
with  its  uncertain  radiance  the  landscapes  of 
our  Earth.  Now  is  the  favourable  moment  for 
making  the  long  journey  to  which  I  have  invited 
you. 

But  what  about  the  means  of  making  it  ?  It  is 
here  the  difficulty  begins,  and  ancient  and  modern 

66 


CYRANO  DE  BERGERAC'S  FLIGHT  TO  THE  MOON 
(From  an  old  engraving). 


ON   THE   WAY  69 

romancers  (including  Cyrano  de  Bergerac)  have  in- 
vented only  improbabilities. 

Perhaps  some  centuries  to  come  the  problem  will 
be  solved,  and  solved  in  the  simplest  way  in  the 
world,  so  let  us  not  worry  about  such  a  trifle. 

Before  the  invention  of  balloons  and  aeroplanes 
no  one  thought  seriously  of  being  able  to  rise  in 
the  air. 

Whoever  finds  out  a  means  of  suppressing  or 
even  diminishing  the  force  of  gravitation,  that 
mysterious  power  which  holds  the  heavenly  bodies 
together  and  keeps  us  fixed  to  the  earth,  will  thus 
enable  men  to  leave  their  planet  and  launch  out 
upon  the  conquest  of  neighbouring  worlds.  And 
the  Moon  will  be  the  first  stage  of  these  inter- 
planetary voyages. 

I  grant  that  it  seems  a  daring  supposition,  but  it 
is  in  no  way  an  absurd  one  from  the  point  of  view 
of  mechanics  and  physics. 

But  as  to  the  physiological  question — that  is 
another  matter. 

The  temperature  of  interplanetary  space  is  near 
absolute  zero — that  is  to  say  that  during  all  its 
course  a  machine  moving  towards  the  Moon  or  a 
shell  fired  at  that  distant  target  would  remain 


70  A   DAY   IN  THE   MOON 

constantly  at  about  450  degrees  (Fahrenheit)  below 
zero. 

Unless  indeed  radium  or  some  similar  substance 
should  give  us  the  means  of  bottling  up  heat,  or 
that  .... 

But  no  !  Let  us  stop  !  This  is  not  a  romance  that 
we  have  to  relate  in  detail.  And  at  the  present 
moment  science  need  not  trouble  about  your  means 
of  travelling  to  the  Moon,  and  every  day  astrono- 
mers explore  this  distant  region  more  easily  than 
the  pioneers  of  our  globe  explore  the  Antarctic. 

The  conditions  of  existence  over  there  are  as  well 
known  as  those  here  on  the  Earth,  and  with  one 
leap  we  can  take  the  selenographers  for  our  guides 
and  come  down  into  the  middle  of  a  lunar  land- 
scape, more  easily  than  you  go  from  London  to 
Paris. 

So  we  make  our  start. 

At  about  six  miles  above  the  surface  of  the  earth 
respiration  becomes  painful  ;  at  about  twelve  miles 
the  air  is  so  rarefied  that  no  animal  "  worthy  of  the 
name "  could  live  there  even  for  the  briefest 
moment.  Organic  germs  like  bacteria  and  vibrios 
would,  however,  survive.  Carried  to  those  lofty 
regions  by  whirlwinds  (which,  by  the  way,  are  not 


ON   THE   WAY  71 

very  frequent  events),  they  would  come  down  again 
uninjured  from  their  perilous  ascent. 

At  1 60  miles  there  is  proof  that  there  is  still  an 
atmosphere,  but  so  attenuated,  so  slight,  that  it  is 
almost  an  abuse  of  language  to  give  the  name  to 
even  the  sum-total  of  the  molecules  to  be  found  there. 

At  a  little  over  8,000  miles — that  is  to  say,  when 
we  have  traversed  a  distance  about  equal  to  the 
diameter  of  the  earth — the  great  globe  that  we  have 
left,  seen  from  this  distance,  would  occupy  about 
40  degrees  of  the  heavens. 

We  pass  the  space  of  another  terrestrial  diameter  ; 
we  continually  increase  our  distance  till  it  is  three, 
four,  five  .  .  .  nine  diameters,  the  Earth  steadily 
diminishing  in  apparent  size.  At  ten  times  this  dis- 
tance it  is  still  a  magnificent  object  in  the  sky  with 
an  apparent  diameter  of  more  than  5  degrees,  and 
with  a  hundred  times  a  greater  surface  than  that 
of  the  Full  Moon  seen  from  the  Earth. 

At  the  same  time  the  size  of  our  satellite  is 
visibly  increasing. 

When  we  have  arrived,  what  will  be  the  apparent 
diameter  of  the  Earth  in  the  heavens  ? 

Here  is  a  problem  in  geometry  that  is  easy 
enough  to  solve. 


72  A   DAY   IN   THE   MOON 

Let  us  suppose,  first  of  all,  that  two  astronomers 
are  at  two  places  the  distance  between  which  is  just 
equal  to  the  radius  (half-diameter)  of  the  earth. 
This  condition,  moreover,  is  easy  to  realise,  as  you 
shall  see  for  yourself. 

If  you  want  to  divide  a  circle,  representing  the 
earth's  circumference,  into  six  exactly  equal  parts, 
all  you  need  do  is  to  take  a  compass  opened 
out  to  the  length  of  the  radius,  and  starting 
from  any  point  of  the  circumference,  mark  off 
in  succession  round  the  circle,  six  points  each  the 
length  of  the  radius  apart.  The  sixth  will  bring 
you  back  to  your  starting-point.  Join  all  these 
points  together  and  to  the  centre,  and  you  will  have 
six  triangles,  of  which  all  the  sides  will  be  equal 
and  therefore  all  the  angles  also  equal  to  each  other. 
Each  angle  at  the  centre  is  clearly  equal  to  one-sixth 
of  360  degrees  (the  angular  measurement  of  the 
whole  circumference),  and  thus  it  will  be  60  degrees 
exactly. 

It  follows  that  two  observers  placed  60  degrees 
apart  on  the  Earth  are  separated,  in  a  straight 
line,  by  a  distance  just  equal  to  the  Earth's  radius. 

In  practice  it  will  be  understood  that  one  can 
take  into  account  the  flattening  of  the  Earth's  shape, 


ON  THE  WAY  73 

and  even  make  the  observations  from  any  two  points 
of  which  the  position  is  exactly  known,  the  rest 
being  only  a  matter  of  calculation  and  the  principle 
being  the  same. 

Let  us  suppose,  then,  our  two  astronomers  are 
posted  at  the  ends  of  a  line  equal  to  the  radius 
of  the  Earth.  You  will  grant  that  it  will  be  easy 
for  each  of  them,  just  at  the  same  moment,  to  direct 
his  instrument  at  the  centre  of  the  Moon  and 
measure  the  angle  at  the  base  of  the  long  triangle 
thus  formed,  the  base  being  the  line  between  them 
on  the  Earth,  and  the  sides  the  lines  joining  each 
observer  to  the  centre  of  the  Moon,  the  line  of 
sight  of  the  observation. 

Very  well.  But  now  our  problem  is  solved,  for 
every  one  knows  that  if  one  adds  together  the 
three  angles  of  a  triangle  the  total  is  180  degrees. 

Let  us  take  an  example.  Our  two  astronomers 
have  obtained  for  their  base  angles,  one  100°,  the 
other  79°. 

100  4-  79  =  179  ;  and  179°  taken  from  180°  = 
i  degree.  The  angle  at  the  summit  of  the  long 
triangle  would  in  this  case  have  exactly  the  value 
of  one  degree. 

Well,  this  experiment  has  been  made  in  several 


74  A   DAY   IN   THE   MOON 

different  ways,  and  astronomers  have  always  found 
a  value  nearly  equal  to  one  degree,  or  exactly 
57  minutes  and  2  seconds. 

As  early  as  the  beginning  of  the  eighteenth 
century  Baron  Krosigk  spent  considerable  sums  in 
determining,  by  the  method  we  have  outlined,  the 
distance  of  the  Moon  from  the  Earth. 

It  was  he  who  first  had  the  idea  of  choosing  the 
Cape  of  Good  Hope  and  the  city  of  Berlin  as  the 
bases  of  operations. 

These  two  points  of  observation  are  situated  just 
over  86  degrees  of  latitude  apart,  and  nearly  on  the 
same  meridian.  It  was  perfect. 

It  was  therefore  decided  that  William  Wagner 
should  remain  in  Europe,  while  Peter  Kolbe  went 
to  the  Cape.  Unfortunately,  the  former  of  these 
two  observers  did  his  part  of  the  business  very  badly, 
and  the  affair  had  to  be  put  off  to  a  later  occasion. 

In  1751  the  Paris  Academy  of  Sciences  took  up 
the  project  again.  The  Abbe  Lacaille  was  sent  to 
the  Cape,  and  Lalande  to  Berlin.  This  time  the 
operation  was  completely  successful.  It  was  the 
first  serious  determination  of  the  distance  between 
the  Earth  and  our  satellite.  Man  had  at  last  made 
the  first  step  in  the  conquest  of  the  heavens. 


ON   THE  WAY  75 

We  may  be  allowed  to  go  a  little  farther  into 
this  matter,  which,  though  it  is  really  so  simple, 
is  often  misunderstood  even  by  educated  persons. 

Let  us  return  to  the  problem  we  have  already 
discussed.  From  the  solution  we  gather  that  an 
observer  placed  in  the  Moon  would  see  the  radius 
of  the  Earth  under  an  angle  of  57  minutes.  Our 
planet  would  of  course  appear  to  him  under  double 
this  angle,  for  as  two  radii  equal  one  diameter,  we 
have  57'  x  2  =  114  minutes — or,  what  comes  to 
the  same  thing,  i°  54'. 

Now,  as  many  times  as  the  angle  i°  54'  is  con- 
tained in  360  degrees,  so  many  times  could  a 
Selenite  place  Earths,  one  touching  the  other,  round 
a  whole  circumference  of  the  sky. 

Let  us  work  out  the  calculation  this  time.  It 
will  only  take  a  moment.  360  degrees,  or  21,600 
minutes,  divided  by  114  minutes  (or  i°  54')  will 
give  us  the  figure  189. 

If  we  suppose  the  orbit  of  the  Moon  to 
be  exactly  circular,  it  will  therefore  be  equal 
to  189  times  the  diameter  of  the  Earth  at  the 
equator. 

The  radius  of  this  orbit,  or  the  distance  of  the 
Earth  from  the  Moon,  will  now  be  obtained  easily 


76  A   DAY    IN   THE    MOON 

by  dividing  this  value  by  twice  3*  14 16,*  or  6'28  in 
round  numbers. 

Now,   189  divided  by  6' 2 8  =30,  nearly  exactly. 

From  which  we  must  conclude  that  the  distance  to 
the  Moon  could  be  filled  up  with  only  thirty  Earths. 

Taking  the  equatorial  diameter  of  our  Earth 
according  to  recent  measurements  as  7,926*6  miles, 
we  have  for  the  approximate  distance  237,798  miles. 

To  simplify  our  calculation  we  have  left  certain 
figures  out  of  account.  Bringing  into  our  reckoning 
the  latest  valuations,  and  not  neglecting  tenths  of  a 
second,  we  get  for  the  measurement  238,833  miles. 

Even  the  error  of  a  second  would  not  make  a 
difference  of  28  leagues  in  the  result.  One  can  see 
very  well  by  this  example  the  precision  obtained 
by  the  methods  of  modern  Astronomy.  We  actually 
know  the  distance  of  our  satellite  to  within  a  few 
miles. 

To  determine  the  size  of  the  Moon  is  now  mere 
child's  play.  It  is  easy  for  us  to  measure  the 
apparent  angular  diameter  of  the  Moon.  It  is  just 
over  31  minutes. 

At   the   same   distance   the  Earth  would  appear 

1  Non-mathematical  readers  may  be  reminded  that  3'i4i6  is  the 
value  of  the  circumference  of  a  circle  whose  diameter  is  I. — Trans- 
lator's Note. 


S   o 

1° 


ON  THE   WAY  77 

about   four   times   larger,    for   we    have   found    its 
diameter  to  be  114  minutes. 

Taking  the  diameter  of  the  Earth  as  the  starting- 
point,  work  it  out  by  the  Rule  of  Three,  and  you 
will  find  for  that  of  the  Moon  about  2,155  miles, 
which  will  give  you  its  volume  as  49  times  smaller 
than  that  of  our  globe. 

It  remains  to  determine  the  mass  and  weight  of 
the  Moon,  but  this  question  would  take  some  time, 
and  we  shall  soon  have  occasion  to  refer  to  it  again. 

Besides,  during  this  long  talk  we  have  made 
serious  progress  towards  our  satellite. 

A  distance  of  238,833  miles  to  traverse :  but 
that  is  not  a  very  great  affair — only  30  times  the 
diameter  of  the  terrestrial  globe. 

A  country  postman  who  makes  a  daily  round  of 
over  1 8  miles  would  walk  in  35  years  as  far  as  the 
whole  distance  between  Earth  and  Moon. 

Our  express  engine-drivers  have  to  their  credit 
much  longer  totals  of  travel. 

An  aviator  who  has  any  respect  for  himself  easily 
does  100  kilometres1  an  hour.      At  this  rate,  and 
supposing   he  could  keep  up  the  same  speed,   he 
would  reach  the  Moon  after  a  flight  of  1 60  days. 
1  62^  miles. 


78  A   DAY   IN   THE    MOON 

On  the  day  when  men  have  at  their  disposal  an 
explosive  powerful  enough  to  give  to  a  shell  an 
initial  velocity  of  12  kilometres2  per  second,  the 
shell  shot  into  the  air  would  never  come  back  to 
Earth.  The  so-called  civilised  nations  could  then 
find  in  the  exercise  of  "  shooting  the  Moon  "  a 
strong  counter-attraction  to  the  folly  of  mutually 
bombarding  each  other.  Under  such  conditions 
the  shots. sent  from  the  Earth  might  serve  as  mail- 
coaches,  and  take  letters  to  our  brethren  the 
Selenites  in  less  than  a  working  day  of  twelve  hours. 

A  despatch  handed  in  at  the  central  office  of  the 
Paris-Moon  post  at  6  a.m.  would  reach  our  satellite 
at  3  in  the  afternoon  of  the  same  day  .  .  .  always 
provided  the  State  did  not  lay  hands  on  the  monopoly 
of  the  new  line. 

The  slightest  delay  would  have  the  most  disas- 
trous results.  The  Moon  would  have  passed  on, 
and  the  mail,  finding  no  one  to  receive  it,  would 
carry  on  its  despatches  to  "  an  unknown  destina- 
tion." 

But  the  best  way  to  realise  how  near  the  Moon 
is  to  us  is  to  compare  the  time  taken  by  light  to 
reach  us  from  that  suburb  of  the  Earth,  and  that 
*  7j  miles. 


DIAGRAM  ILLUSTRATING  THE  DISTANCE  OF  THE  MOON  FROM  THE 

EARTH. 
79 


ON   THE  WAY  81 

which  it  takes  to  pass  across  the  spaces  that  separate 
us  from  the  Sun,  the  planets,  and,  above  all,  the  stars. 

While  a  ray  of  light  from  the  Pole  Star  reaches 
us  after  a  long  journey  of  46  years,  and  takes 
more  than  four  years  to  "work  off"  the  tre- 
mendous distance  that  divides  us  from  our  neigh- 
bour Alpha  Centauri,  we  know  that  the  luminous 
vibrations  from  the  Sun  certainly  do  not  take 
more  than  9  minutes  to  arrive  here. 

Now,  light,  as  you  know,  moves  at  the  rate  of 
186,000  miles  a  second.  In  a  little  more  than 
one  second — say  about  the  time  it  takes  to  count 
"  two " — it  crosses  the  abyss  that  separates  us 
from  the  Moon. 

This  neighbouring  globe,  49  times  smaller  than 
our  own,  is  therefore  really  at  arm's  length.  It 
moves  in  our  wake,  and  shares,  up  to  a  certain  point, 
our  destiny  in  the  universe.  A  politician  might  say 
that  it  is  within  our  "  sphere  of  influence  "  ;  and  this 
nearness  is  enough  to  explain  why  astronomers  in 
general  study  it  so  little,  and  yet  know  it  so  well. 

But  we  have  arrived.  Our  imaginary  vehicle 
sets  us  down. 

Let  us  open  our  eyes  and  lose    nothing   of  the 

strange  spectacle  presented  to  our  gaze. 
6 


VI 
LUNAR    LANDSCAPES 

IT  is  still  night  in  the  region  in  which  we  have 
landed  on  the  surface  of  the  Moon. 

The  sky  sparkles  with  incomparable  splendour. 
The  eye  can  distinguish  in  it  thousands  and  thousands 
of  stars.  Not  even  the  glories  of  a  tropical  night 
can  give  any  idea  of  what  night  on  the  Moon 
must  be. 

But  soon  the  Sun  will  appear.  There  is  no  dawn 
to  herald  it,  but  already  there  is  rising  in  the  east 
a  long,  spindle-shaped  trail  of  whiteness — it  is  the 
zodiacal  light,  ten  times  more  brilliant  than  with  us. 

For  hours  this  false  dawn  rises  higher  in  the  sky; 
its  tints  of  phosphorescent  colours  are  brighter 
and  brighter  from  the  summit  to  the  base  ;  in  the 
midst  of  the  enormous  cone,  all  aglow  with  green 
and  opal,  there  gleams  a  resplendent  star  :  it  is  the 
beautiful  Venus,  hardly  recognisable  amid  its  mantle 

of  light. 

82 


< 


LUNAR   LANDSCAPES  83 

But  already  the  fine  rays  of  the  Sun's  corona 
are  heralding  the  day-star.  For  a  few  minutes  the 
chromosphere  is  in  sight,  marking  with  a  red  glow 
the  summits  of  the  high  mountain  peaks. 

Then  all  of  a  sudden  blue  rays  of  light,  so 
strong  that  the  eye  cannot  endure  them,  dart  from 
the  distant  horizon.  And  now  on  all  sides  isles  of 
brightness  seem  to  rise  up  around  us  as  the  summits 
catch  the  sunlight.  The  day  has  come. 

Where  have  we  landed  ? 

Let  us  look  attentively  at  our  surroundings. 
Here  aerial  perspective  is  unknown,  and  the  isles 
of  light  seem  to  mark  out  a  large  ellipse  on  the 
background  of  a  black  expanse. 

Evidently  we  are  looking  down  on  the  summits 
of  a  vast  circuit  of  heights,  nearly  hexagonal,  if  we 
may  judge  by  the  arrangement  of  the  outstanding 
spots  of  brightness.  We  are  watching  the  dawn 
of  the  lunar  day  from  the  lofty  rampart  of  a  "  crater" 
known  as  Copernicus. 

"  What  !  Do  you  mean  to  say  this  enormous 
circle  of  fifty  miles  in  diameter  could  be  the  crater 
of  a  volcano  ?  "  Well,  this  clearly  goes  beyond  all 
probability,  but  the  old  astronomers  did  not  look 
at  things  quite  so  closely. 


84  A   DAY   IN   THE   MOON 

So  long  as  there  was  a  roughly  circular  rampart, 
generally  resembling  in  appearance  our  terrestrial 
volcanoes,  the  comparison  was  inevitable  ;  and  as  it 
is  natural  for  the  human  mind  to  assign  a  cause  to 
the  effects  it  observes  without  waiting  long  over  it, 
an  explanation  was  soon  found  for  those  huge 
mountain  systems,  of  which  the  smallest  telescope 
will  show  you  specimens  by  hundreds. 

Provide  yourself  with  higher  powers,  and  you 
will  soon  remark  that  a  good  many  of  these  lunar 
"  craters  "  have  a  central  mountain  inside  of  them. 

This  peculiarity  did  not  escape  the  notice  of  the 
first  selenographers,  and  here  is  how  they  reasoned 
with  regard  to  it  : 

We  know  by  calculation  that  the  intensity  of 
gravitation  is  about  six  times  less  on  the  Moon 
than  it  is  with  us.  Let  us  suppose,  which  is  indeed 
quite  likely,  that  the  explosive  effects  of  interior 
gases  are  as  violent  there  as  on  the  Earth.  It  follows 
that  volcanic  debris  would  be  thrown  six  times 
farther.  The  central  mountain  was  thus  originally 
the  active  cone  of  the  volcano,  and  everything  is 
explained. 

Thus,  when  the  course  of  ages  had  not  yet 
thickened  the  surface  crust,  and  when  the  liquid  or 


LUNAR   LANDSCAPES  85 

molten  interior  communicated  with  the  outside  by 
the  blow-holes  of  the  central  fire,  these  eruptive 
openings  vomited  into  space  and  to  prodigious 
heights  the  inner  substances  of  the  Moon.  Rocks, 
volcanic  matter  of  all  kinds,  vitrified  minerals,  dust 
and  hot  ashes — all  this  came  from  the  underlying 
beds  through  the  central  vent,  and  was  deposited 
in  a  huge  circle  at  a  greater  or  less  distance  from 
the  volcano. 

That  there  are  in  the  Moon  some  small  craters 
*  formed  in  this  way  seems  beyond  doubt,  but  the 
volcanic  theory  of  the  lunar  circles  does  not  explain 
everything. 

One  might,  first  of  all,  object  that  it  is  very 
strange  that  we  generally  do  not  find  in  the  interior 
of  these  great  circles  any  serious  inequalities  of  the 
ground,  any  mountain  resembling  those  of  the  outer 
rampart.  One  would  expect  to  find  regular  con- 
centric rings  at  various  distances  from  the  centre, 
marking  the  progressive  decrease  of  the  eruptive 
phenomena  in  the  course  of  geological  time. 

But  there  is  nothing  of  the  kind  !  And,  what 
is  still  more  to  the  purpose,  the  central  peak  has 
not  often  a  form  reminding  us  of  the  mouths  of 
our  volcanoes. 


86  A   DAY   IN   THE    MOON 

And  then,  who  can  believe  that  this  elevation  in 
the  interior,  always  of  lower  height  than  the  moun- 
tains around  it,  could  have  thrown  out  masses  of 
matter  to  such  a  distance  that  they  are  piled  up 
into  these  enormous  circular  ramparts,  the  height 
of  which  often  exceeds  that  of  the  loftiest  summits 
of  the  Alps  ? 

And  an  example  of  this  is  before  our  eyes. 
Copernicus  is  the  monarch  of  the  ring-shaped 
mountains  of  our  satellite,  the  king  of  the  ringed 
•plainSy  to  use  a  favourite  expression  of  English 
selenographers,  an  expression  greatly  to  be  preferred 
to  the  old  grotesque  and  fanciful  terminology  of 
the  "  craters." 

There  are  more  than  twenty-five  miles  between  us 
and  its  centre,  as  we  stand  perched  on  a  point  of 
its  rampart  towering  some  13,000  feet  above  its 
interior  plain. 

Including  its  external  slopes,  the  diameter  of  this 
circular  mountain  is  nearly  sixty  miles.  From  one 
side  of  Copernicus  to  the  other  there  is  about  the 
same  distance  as  from  Paris  to  Orleans.1 

An   attentive  observer   might  pass  all  his  life  in 
studying   Copernicus.      He    would    every    day  find 
1  Or  from  London  to  Portsmouth. —  Translator's  Note. 


LUNAR    LANDSCAPES 


new  details  in  it,  and  this  marvellous  object  includes 
all  the  interesting  characteristics  of  the  other  moun- 
tain rings,  several  of  which,  however,  exceed  it  in 
extent. 


Petavius,  for  example,  measures  100  miles  from 
one  side  to  the  other,  and  Manginus  and  Lagrange 
show  the  same  dimensions.  Herschel  presents  a 
diameter  of  90  miles;  Gauss  is  still  larger — no 


88  A   DAY   IN   THE   MOON 

miles  ;  Humboldt  is  112^  miles  across,  and  Clavius 
exceeds  this  width  by  more  than  1 1  miles. 

And  then  there  are  the  giant  circles  of  Grimaldi, 
Stoefler  and  Maurolycus,  of  which  the  mean  diameter 
reaches  150  miles. 

If  one  could  transfer  Maurolycus  to  France,  placing 
its  centre  at  Orleans,  the  circular  ramparts  that 
form  its  boundary  would  pass  near  Le  Mans,  Tours, 
Nevers,  and  Saint-Denis.  Paris,  Melun,  Sens,  La 
Charite,  Bourges,  Blois,  and  Chartres  would  be 
hidden  away  in  its  interior.1 

A  strange  kind  of  crater  indeed,  the  bottom  of 
which  is  so  very  like  the  great  plains  of  the  Beauce 
and  the  Sologne,  where  one  might  walk  for  hours  and 
hours  without  seeing  any  mountain  on  the  horizon. 

1  It  may  help  the  English  reader  to  note  that  similarly  if  the 
centre  of  Maurolycus  were  placed  at  Oxford,  its  rampart  of  mountains 
would  run  in  a  huge  circle  which  to  the  north-west  would  lie  just 
beyond  Wolverhampton  and  the  Potteries,  and  would  sweep  round 
by  Burton-on-Trent  to  Peterborough,  pass  a  few  miles  east  of 
Cambridge  and  through  Chelmsford,  cross  the  Thames  below 
London,  about  Gravesend,  pass  through  Ashdown  Forest,  in  Kent, 
and  reach  the  sea  at  Littlehampton ;  then  pass  through  the  middle 
of  the  Isle  of  Wight,  reach  the  mainland  again  near  Christchurch, 
take  in  the  whole  of  Salisbury  Plain,  and  by  the  Mendip  Hills 
reach  the  shore  of  the  Bristol  Channel  opposite  Newport,  and  then 
curve  through  the  south-east  borders  of  Wales  and  back  to  the 
Pottery  district.  Among  the  places  within  its  mountain  ring  would 
be  London,  Birmingham,  Bristol,  Southampton,  and  Portsmouth. — 
Translator's  Note. 


LUNAR   LANDSCAPES  89 

Through  their  having  failed  to  make  any  exact 
measurement  of  these  enormous  formations,  the  old 
astronomers  allowed  themselves  to  be  misled  by 
appearances. 

But  while  we  are  making  these  explanations  the 
Sun  has  entirely  risen.  On  our  earth  in  latitudes 
about  half-way  between  Pole  and  Equator,  the  time 
the  Sun  takes  to  show  his  complete  disc,  from  the 
appearance  of  its  upper  margin  till  its  lower  edge 
just  touches  the  horizon,  is  only  2|-  minutes.  On 
the  Moon  it  takes  no  less  than  an  hour  for  the 
same  thing  to  take  place  .  .  .  and  you  can  see  the 
reason  of  this. 

Our  satellite  turns  on  its  axis  about  28  times 
less  quickly  than  the  Earth,  and  everything  is  in 
proportion  to  this  slow  rotation. 

From  the  time  of  sunrise  a  period  of  354  hours 
of  light  goes  by,  and  then  comes  a  night  of  equal 
duration. 

Such  is  the  length  of  the  lunar  days.  It  has  always 
seemed  to  me  an  excellent  illustration  of  the  rela- 
tive nature  of  time. 

Our  divisions  of  it  into  hours,  minutes,  and 
seconds  are  obviously  arbitrary,  and  based  upon  the 
return  of  the  Sun  to  the  same  point  in  the  heavens. 


90  A   DAY   IN   THE   MOON 

Now,  this  interval  between  two  of  its  passages 
across  the  meridian  depends  on  our  movement  of 
rotation.  And  just  as  we  do  not  think  of  basing 
our  measures  of  time  and  our  calendar  on  the 
rotation  and  revolution  of  Jupiter,  so  the  Selenites 
would  have  no  reason  for  founding  theirs  on  our 
terrestrial  calendar. 

Thus,  when  I  promised  to  let  you  pass  a  day 
on  the  Moon,  I  meant  to  speak  of  a  true  lunar 
day,  so  we  have  more  than  three  hundred  hours 
before  us,  in  which  to  visit  our  satellite  and  carry 
out  excursions  that  a  terrestrial  explorer  might 
envy. 

It  is  not,  however,  the  fact  that  days  as  long  as 
this  are  entirely  unknown  in  our  world.  Our  polar 
regions  give  us  some  that  last  even  longer,  but  the 
Sun  of  these  far  northern  lands  is  a  smoky  torch 
compared  to  that  which  shines  like  an  electric  arc 
light  in  the  lunar  skies. 

You  can  see  for  yourself  that,  though  the  Sun 
is  hardly  risen  above  the  horizon,  you  can  already 
distinguish  all  the  details  of  this  fantastic  natural 
scenery  that  seems  created  for  Titans. 

Now  we  notice  the  five  central  mountains  of  the 
great  ring,  imposing  masses  whose  summits  gleam 


LUNAR    LANDSCAPES  91 

with  a  harsh  glare,  while  their  bases  are  still  plunged 
in  the  shadows  of  a  night  that  is  never  absolutely 
black  but  is  illuminated  by  the  earth-shine. 

Over  there,  on  the  horizon,  are  the  glittering 
higher  summits  of  the  opposite  rampart,  and  the 
loftiest  of  them  rears  its  terminal  cone  to  the  height 
of  more  than  13,000  feet — I  nearly  said  "into  the 
air." 

But  here  we  have  to  change  our  terminology 
and  our  literary  phrases.  The  absence  of  air,  or 
of  any  gas  that  can  be  breathed,  completely  alters 
our  way  of  looking  at  things. 

On  the  Moon  there  is  no  aerial  perspective. 
Everything  glitters  with  dazzling  light.  Its  rays 
strike  on  the  projecting  rocks  with  an  absence  of 
all  gradation  that  gives  them  an  unreal  look. 
Things  near  and  far  seem  confusingly  alike,  and 
the  eye  is  not  guided  in  its  judgment  of  distance 
by  any  variation  of  tint. 

The  clouds  which  temper  the  effect  of  the  sun- 
light, which  rise  from  the  valleys,  assume  definite 
shapes,  float  hither  and  thither  in  the  ocean  of  air 
carrying  with  them  the  dreams  of  poetic  souls,  and 
which  shroud  the  mountain  crests  and  give  varia- 
tions of  dull  grey  or  bright  colour  to  the  sky — all 


92  A   DAY   IN   THE   MOON 

this  is  unknown  in  the  lunar  landscape.  And  this 
only  half-surprises  us,  for  as  soon  as  ever  we  reach 
the  Moon  we  recognise  that  air  and  water  are 
alike  unknown  to  the  lands  on  which  we  have  set 
foot. 

But  the  first  selenographers  were  far  from 
suspecting  this.  Otherwise  they  would  not  have 
given  to  these  vast  desolate  plains  such  ill-chosen 
names  as  "  sea,"  "  ocean,"  and  "  marsh." 

The  stony  desert  in  front  of  us  out  of  which 
Copernicus  rises  is  known  as  the  "  Ocean  of 
Storms."  l  We  shall  traverse  the  extremity  of  it, 
its  borders,  as  we  continue  our  journey  northwards. 

The  absence  of  any  atmosphere — a  fact  definitely 
established  by  modern  astronomers — explains  another 
very  characteristic  peculiarity  of  this  world  that  is 
so  unlike  our  own. 

On  the  Earth  the  Sun's  rays  reach  us  after  a 
long  passage  through  the  layers  of  the  atmosphere. 
There  is  thus  what  we  may  call  a  selective  absorp- 
tion of  some  of  them,  a  winnowing  out,  so  to  say, 
of  the  different  colour  rays,  many  of  which  are 
lost  in  the  meshes  of  this  new  kind  of  sieve. 

The  shortest  light- waves,  those  of  violet  and 
1  Oceanus  Procellarura. 


COPERNICUS. 


92! 


LUNAR    LANDSCAPES  93 

blue,  are  delayed  on  the  way,  and  only  the  longer 
radiations  near  the  red  end  of  the  spectrum  reach 
us  easily. 

Do  you  want  a  palpable  proof  of  this  ?  Watch 
the  sunrise  and  notice  the  general  tone  of  the  land- 
scape up  to  midday. 

At  dawn  the  east  is  bright  with  the  rosy  tint  of 
which  the  poets  sing.  The  clouds  are  edged  with 
lines  of  scarlet.  All  white  surfaces  reflect  the  same 
colours.  Then  the  day-star  appears  and  the  red  is 
mingled  with  other  parts  of  the  spectrum,  giving  at 
first  violet  tints  and  later  on  more  yellow  tones. 

As  the  rays  of  the  sun  rising  above  the  horizon 
pass  through  a  less  dense  body  of  air,  the  shorter 
light-waves  reach  us  more  easily,  and  it  is  towards 
midday  that  we  receive  the  most  of  them. 

At  that  time  of  day,  especially  in  tropical 
countries,  the  shadows  of  things  assume  quite  plainly 
the  complementary  tints  of  these  rays. 

Such  of  my  readers  as  live  in  Algeria  or  Tunisia, 
or  in  Egypt  or  India,  can  see  this  for  themselves 
with  the  help  of  a  photographic  apparatus.  Let 
them  look  at  the  image  of  a  landscape  on  the  dull 
surface  of  the  focussing  glass,  and  they  will  see  that 
the  shadows  are  all  quite  blue. 


94  A   DAY   IN   THE   MOON 

On  the  Moon,  where  there  is  not  even  the 
slightest  trace  of  an  atmosphere,  the  Sun's  rays  do 
not  pass  through  any  filtering  screen  before  reach- 
ing the  ground,  and  it  is  this  blue  colour  that  gives 
its  dominant  note  to  the  landscape.  And  this  is 
why  the  Sun  seen  thence  looks  like  an  electric  arc, 
a  gigantic  lamp  of  glittering  blue  ;  a  gleaming  mass 
whose  fierce  blinding  light  adds  all  the  more  to  the 
impression  of  coldness  produced  by  the  sight  of  a 
world  rigid  in  death — unreal  and  yet  existing, 
gloomy  yet  full  of  light,  blue  and  black  at  the 
same  time. 

Nevertheless  if  we  look  more  closely  we  shall 
find  there,  as  on  the  Earth,  a  whole  scale  of  colours. 
In  the  midst  of  this  mountain-ring  now  partly 
bathed  in  the  Sun's  rays,  besides  the  dominant  note 
of  blue,  and  half  drowned  in  it,  you  can  make  out 
the  various  shades  of  minerals  and  rocks  like  those 
of  our  Earth. 

And  here  we  may  remark  how  little  is  the  worth 
of  the  assertions  made  by  certain  astronomers  who 
repeat  the  follies  of  their  predecessors,  and  tell  us 
that  on  the  Moon  there  is  no  medium,  that  every- 
thing is  either  black  or  full  of  light,  accordingly  a« 
the  Sun  is  absent  or  darts  its  rays  upon  it. 


LUNAR    LANDSCAPES  95 

No !  Objects  on  the  Moon  must  keep  their 
own  colours,  tinged  with  blue  of  course,  for  that 
is  the  general  tone  of  the  sunlight  on  these  wild 
landscapes.  The  angle  of  the  precipices  on  which 
it  falls,  the  slopes  of  the  ground,  the  height  of  the 
Sun — all  these  causes  combine  to  produce  half-tints, 
diversified  tones,  and  changing  effects  as  on  the 
Earth. 

During  the  night  on  the  hemisphere  of  the  Moon 
that  is  constantly  turned  towards  us,  our  planet 
serves  as  a  moon  to  its  satellite — an  enormous  disc 
reflecting  a  light  fourteen  times  more  intense  than 
that  with  which  fair  Diana's  orb  illuminates  our 
landscapes,  even  when  at  the  full  and  at  its  maxi- 
mum brightness  it  passes  through  the  zenith  and 
sends  down  its  soft  light  into  the  smallest  clefts  of 
our  deep  valleys. 

When  the  "  Full  Earth  "  sends  back  to  the  Moon 
the  reflection  of  the  sunlight  and  our  own  atmo- 
sphere adds  to  the  effect  of  this  fierce  glare,  it  is 
like  broad  day  on  the  surface  of  our  satellite.  The 
intense  shadows  of  the  mountains  are  less  dark, 
and  absolute  blackness  can  find  a  refuge  only  in 
the  deepest  chasms. 

Even   in   the   midst  of  the   long  lunar   day  Sun 


96  A   DAY   IN   THE   MOON 

and  Earth  act  as  allies  and  combine  their  light  to 
soften  the  crudity  of  tones  and  colours. 

This  is  a  point  that  we,  men  of  the  Earth,  had 
not  till  now  realised,  but  which  our  first  excursion 
shows  us  in  the  clearest  fashion. 

And  nevertheless  there  can  be  no  possible  com- 
parison with  the  landscapes  of  the  Earth.  Cast 
your  eyes  over  and  beyond  these  frightful  preci- 
pices, those  steep  declivities  broken  only  by  two  or 
three  terrace-like  slopes  of  debris,  and  what  presents 
itself  to  your  dazzled  eyes  is  above  all  a  spectacle 
of  the  most  awful  desolation.  There  is  not  a  patch 
of  moss,  not  a  heath-grown  ledge,  to  soften  the 
rocky  ridges  and  sharp-cut  edges  of  these  abrupt 
surfaces ;  not  even  the  lowest  form  of  plant-life, 
not  a  lichen,  to  attenuate  the  wild  aspect  of  the 
landscape  and  give  it  even  the  slightest  appearance 
of  life. 

And  now  we  can  better  understand  that  passage 
in  which  Nasmyth,  most  enthusiastic  of  seleno- 
graphers,  tells  us  how  the  whole  landscape  as  far 
as  the  eye  can  reach  is  the  realisation  of  a  dream 
of  the  most  awful  desolation  and  of  nature  without 
life.  It  is  not  even  a  dream  of  death,  but  it  is  the 
vision  of  a  world  where  life  has  never  existed. 


LUNAR    LANDSCAPES  97 

And  yet  who  can  assert  that  in  the  far-off  times 
of  the  Earth's  first  ages  the  Moon  was  not  the 
abode  of  living  beings  ? 

If  we  had  at  our  disposal  the  "  time  machine " 
of  Mr.  H.  G.  Wells,  the  romancer  who  deals  in 
the  most  astounding  of  improbabilities,  we  might 
witness  a  spectacle  of  much  the  same  kind  .  .  . 
while  looking  at  our  Earth. 

One  or  two  turns  of  a  crank  and  the  flywheel 
of  the  machine  begins  to  revolve. 

Ten  million  years  have  passed  by  with  the  speed 
of  lightning  ;  twenty  millions  ;  fifty  ;  eighty  ;  a 
hundred  million  years. 

Let  us  stop  the  machine  and  take  a  look. 
In  the  sky  the  day-star  has  become  pale.     The 
last  fires  of  our  glorious  Sun  are  burning  down. 

Its  ruddy  rays  still  reach  the  Earth,  but  alas ! 
it  is  only  to  light  up  the  most  mournful  of 
pictures. 

The  Earth's  atmosphere  exists  no  longer.  The 
rocks  and  minerals  and  calcareous  compounds  have 
absorbed  it  little  by  little.  The  waters  of  the 
oceans  have  permeated  the  underlying  strata,  and 
the  cold  of  interplanetary  space  has  frozen  up  the 
last  traces  of  moisture.  On  the  desert  ground  no 
7 


98  A   DAY   IN   THE   MOON 

crop  any  longer  ripens.  The  Earth  has  become 
sterile.  Forests  and  prairies  have  all  disappeared. 

At  the  beginning  of  this  slow  but  continuous 
cooling  down  of  the  earth  the  human  race  in  a 
body  had  taken  refuge  in  the  equatorial  zone, 
where  a  dwarfed  vegetation  had  replaced  the 
abundant  flora  of  the  tropics. 

Some  millions  of  years  more  and  only  a  vegeta- 
tion like  that  of  the  polar  regions  could  withstand 
the  glacial  climate. 

One  by  one  most  species  of  animals  became 
extinct.  To  hold  out  somewhat  longer  the  last 
families  of  the  human  race  dug  into  shafts  and 
deep-lying  underground  tunnels,  and  it  is  there 
that  in  the  last  of  these  catacombs  their  frozen 
bones  are  now  lying. 

Ten  million  years  more  and  an  explorer  traversing 
this  silent  desolation  might  well  believe  he  had 
good  reason  to  think  of  the  Earth  as  Nasmyth  does 
of  the  Moon. 

Every  trace  of  organic  life  would,  in  fact,  have 
disappeared.  Our  monuments,  our  powerful 
machines,  all  the  products  of  our  industry  and 
civilisation,  would  have  been  reduced  to  dust  and 
gone  back  to  the  earth,  and  not  one  particle  would 


LUNAR   LANDSCAPES  99 

remain  to  reveal  the  previous  existence  of  life  on 
our  planet. 

Such  an  end  of  the  Earth  and  its  inhabitants 
is  the  normal  manner  of  death  for  the  worlds  in 
stellar  space.  But  poor  humanity  may  vanish 
hence  in  some  frightful  catastrophe,  and  science, 
even  in  the  guise  of  the  Wells  machine,  is  power- 
less to  reveal  to  us  the  lot  that  awaits  us. 

However  this  may  be,  this  account  of  the  end 
of  our  planet  seems  to  apply  very  well  to  the 
lunar  world.  Our  satellite  is  49  times  smaller 
than  the  Earth.  It  has  therefore  cooled  down  more 
quickly  ;  and  though  its  days  are  materially  longer, 
the  phases  of  its  life  among  the  heavenly  bodies 
have  been  hurried  through  more  rapidly  than  ours. 

At  the  present  time  there  is  nothing  to  justify 
us  in  believing  that  life  exists  on  the  surface  of 
the  Moon,  and  the  astronomers  of  our  Earth  have 
explored  every  corner  of  it. 

The  smallest  angular  space  that  the  human  eye 
can  appreciate  is  about  half  a  minute.  A  magni- 
fying power  of  30  diameters  enables  us  to  see 
a  spot  a  second  in  diameter.  Now  an  angular 
distance  of  a  second  on  the  Moon  represents  about 
1,960  yards.  This  is  the  limit  of  visibility  for 


ioo  A  DAY   IN  THE   MOON 

small  telescopes.  But  when  one  adapts  to  a 
more  powerful  instrument  a  magnifier  of  300 
diameters,  the  eye  can  distinguish  details  measuring 
only  197  yards.  With  the  power  of  600  one  can 
perceive  an  object  measuring  98^  yards.  This 
would  be  reduced  to  59  yards  and  29^-  yards  if 
we  used  powers  of  1,000  and  2,000  diameters. 

In  practice  we  have  unfortunately  to  reckon 
with  an  element  of  some  importance,  the  atmo- 
spheric waves,  of  which  our  telescopes  also  magnify 
the  effects  in  the  most  distressing  fashion.  The 
training  of  the  observer,  the  practice  of  the  eye, 
and  the  diameter  of  the  objective  have  also  to  be 
taken  into  account.  There  has  often  been  talk  of 
powers  of  2,000  being  adapted  to  large  telescopes. 
But  in  the  opinion  of  all  selenographers  these 
high  powers  give  no  result  when  applied  to  the 
study  of  the  Moon,  and  as  a  rule  we  have  to 
content  ourselves  with  a  magnifying  power  of  400. 

But  here  another  question  arises,  and  we  must  be- 
ware of  falling  into  the  mistake  of  certain  popular 
astronomers  who  reproduce  an  argument  of  Arago. 

This  astronomer  tried  to  make  out  that  to 
magnify  a  portion  of  the  Moon's  surface  2,000 
times  was  the  same  thing  as  to  bring  it  2,000 


LUNAR   LANDSCAPES  101 

times  nearer,  and  consequently  to  see  it  just  as  we 
see  an  object  on  earth  120  miles  distant  from  us 
— in  the  same  way,  for  instance,  as  a  tourist  sees 
the  mountains  of  Corsica  from  the  heights  above 
Monaco  (distance,  1 90  kilometres  =  1 1 8  J  miles.) 

Well,  this  reasoning  loses  all  its  force  as  soon  as  we 
try  to  apply  it  to  an  object  in  the  heavens  elevated 
above  the  horizon  and  anywhere  near  the  zenith. 

In  this  case,  as  a  matter  of  fact,  our  line  of 
sight  passes  through  a  depth  of  air  equivalent  only 
to  that  which  separates  us  from  an  object  placed 
at  a  distance  of  about  6  miles  on  the  earth,  whilst 
when  we  look  at  Corsica  from  Monaco  or  the 
cone  of  Etna  from  Malta  the  rays  of  light  come 
to  us  weakened  by  passing  through  a  mass  of  air 
that  is  twenty  times  denser.  This  more  or  less 
opaque  screen,  agitated  by  strong  currents,  in  con- 
tinual movement  and  laden  with  dust  and  vapour, 
deadens  the  tints  and  blots  out  the  details  so 
that  the  comparison  is  worthless. 

What  should  be  said  is  that  with  a  magnifying 
power  of  400 — and  experience  is  there  to  prove  it — 
a  trained  eye  can  distinguish  on  the  Moon  an  object 
135  metres  (or  443  feet)  in  diameter,  and  this 
magnifying  power  is  ordinarily  used  by  astronomers. 


102  A  DAY   IN   THE   MOON 

In  exceptional  cases — with  an  abnormally  clear 
and  calm  atmosphere — we  can  use  powers  of  600 
and  observe  on  the  Moon  spots  and  objects  only 
90  metres  (  =  295  feet)  in  diameter,  whilst,  accord- 
ing to  Dr.  Weineck,  in  the  case  of  our  photo- 
graphic maps  of  the  Moon  we  have  to  be  content 
with  making  out  spots  of  700  metres  (=  2,296 
feet)  in  diameter. 

The  superiority  of  telescopic  vision  over  photo- 
graphy is  still  more  marked  when  it  is  a  matter 
of  revealing  a  long  narrow  object  such  as  a 
geological  fault  or  a  crack  in  the  ground.  With 
a  magnifying  power  of  400  we  can  distinguish 
clefts  in  the  surface  that  are  only  40  to  50  metres 
wide  (i.e.  131  to  1 64  feet). 

A  great  building  like  one  of  our  cathedrals,  a 
railway-station,  a  village,  a  regiment  on  the  march, 
would  therefore  be  quite  visible.  But  no  one 
has  ever  observed  such  signs  of  civilisation.  We 
are,  however,  thus  in  a  good  position  for  studying 
the  question  of  changes  in  the  surface  formation 
of  the  Moon,  and  astronomers  have  not  failed  to 
do  this.  .  .  .  But  time  is  running  on,  and  this 
question  will  come  up  naturally  in  the  course  of 
our  intended  excursions. 


VII 
ON   THE   MOON 

BUT  we  must  see  about  leaving  this  elevated  point 
of  observation  overlooking  the  mountain  crests  of 
this  circle  of  Copernicus,  and  making  our  way  down 
to  visit  the  great  plains  that  the  sunlight  is  now 
bathing  in  its  slanting  rays. 

It  is  not  easy  to  fix  upon  the  line  of  easiest 
descent.  Everywhere  the  mountain  sides  go  down 
abruptly  at  a  startling  angle  of  inclination,  then 
rising  up  to  minor  outlying  summits  they  join  on  to 
subsidiary  ranges  or  folds  of  the  surface  that  are 
arranged  round  Copernicus  like  the  spokes  of  an 
enormous  wheel. 

We  cannot  dream  of  reaching  the  region  to  the 
south,  of  which  you  can  distinguish  the  deep 
gorges  and  frightful  precipices  where  the  rocks  fall 
noiselessly  and  the  avalanches  of  stones  awake  no  echo. 

Let  us  rather  make  our  way  to  the  north  side  ; 

the  ground  there  looks  more  practicable. 

103 


io4  A   DAY   IN   THE   MOON 

But  take  note  of  this — you  will  recollect  that  the 
lunar  globe  has  an  attraction  six  times  less  than  that 
of  our  terrestrial  globe.  Here  is  the  explanation 
of  that  sense  of  lightness  which  is  so  thoroughly 
characteristic  of  the  place. 

Have  you  ever  thought  about  the  cause  of 
weight  ?  It  is  essentially  only  a  variety  of  attrac- 
tion. It  seems  that  the  fall  of  an  apple  was  enough 
to  start  a  train  of  thought  that  put  the  great 
mathematician  and  philosopher  Newton  on  the 
track  of  the  discovery  that  the  heavenly  bodies 
attract  each  other  in  the  same  way  that  the  Earth 
draws  falling  bodies  to  its  surface.  Later  on  he 
was  enabled  by  a  study  of  the  movement  of  the 
Moon  in  its  orbit  definitely  to  establish  those  great 
laws  of  attraction  which  are  the  basis  of  the 
mechanism  of  the  heavens.  "  Things  work  out," 
said  Newton,  "  as  though  bodies  attracted  each  other 
according  to  their  mass,  that  is  to  say,  according  to 
the  quantity  of  matter  they  contain." 

The  weight  of  a  body  is  not  therefore  an  inherent 
quality  of  matter. 

Let  us,  for  instance,  imagine  a  single  atom  existing 
by  itself  in  the  world  and  in  space.  There  is 
nothing  that  attracts  this  atom.  Therefore  it  has 


ON   THE   MOON  105 

no  weight.  Place  in  its  presence  a  small  mass  of 
other  atoms.  Immediately  the  two  unequal  masses 
tend  to  approach  each  other,  and  weight  comes  into 
existence. 

This  attracting  force  of  weight  is  therefore  in  the 
highest  degree  something  variable  according  to  the 
masses  of  bodies.  The  mass  of  the  Moon  being 
much  less  than  that  of  the  terrestrial  globe,  one  can 
very  easily  see  that  a  stone  transferred  to  our 
satellite  would  there  be  less  strongly  attracted,  and 
would  therefore  weigh  less. 

Take,  for  instance,  a  rock  which  you  would  judge 
to  weigh  exactly  100  pounds  here  on  the  earth. 
Lift  it  in  your  arms  on  the  Moon,  and  you  would 
feel  as  if  you  were  holding  up  barely  20  pounds. 

And,  wonderful  to  say,  there  was  no  need  for 
astronomers  to  make  an  excursion  to  the  Moon  in 
order  to  determine  the  weight  of  bodies  on  its 
surface  and  even  to  weigh  the  Moon  itself.  There 
are  plenty  of  ways  of  doing  this,  and  the  most  simple 
to  grasp  is  one  that  can  be  easily  understood  by 
everybody. 

If  the  Moon  were  as  heavy  as  the  Earth,  the  two 
bodies  would  equally  attract  each  other,  and  both 
would  begin  to  revolve  round  their  common  centre 


io6  A   DAY   IN   THE   MOON 

of  gravity,  that  is  to  say,   round  a  point  situated 
just  half-way  between  the  Earth  and  the  Moon. 

But  as  a  matter  of  fact  their  masses  are  unequal, 
and  at  the  moment  when  the  Moon  is  before  the 
Earth  on  its  orbit  it  is  easy  to  discover  by  observa- 
tion that  we  are  drawn  forward  just  a  little  by  our 
satellite.  The  amount  of  this  displacement,  cal- 
culated by  the  apparent  displacement  of  the  Sun 
in  the  heavens,  is  about  2,300  miles,  or  nearly  the 
eighty-first  part  of  our  distance  from  the  Moon. 
Hence  it  can  be  inferred  that  the  mass  of  the  Earth 
is  8 1  times  greater  than  that  of  the  Moon  ;  at  any 
rate,  it  is  most  certainly  something  between  the 
numbers  80  and  83. 

Let  us  follow  out  the  consequences  of  this  line  of 
reasoning.  Newton  has  shown  under  his  second 
law  that  attraction  diminishes  in  proportion  to 
distance.  We  can  show  this  even  here  on  our 
Earth  where  bodies  weigh  less  the  farther  they  are 
from  its  centre.1  If,  then,  the  Earth  and  the  Moon 
were  the  same  size,  a  stone  on  our  satellite  would 
weigh  8 1  times  less  than  here  on  earth.  But  this 


1  Such  experiments  are  of  course  made  not  by  balancing  weight 
against  weight  in  scales,  but  by  the  use  of  spring  balances. — 
Translator's  Note. 


REGION  OF  THE  LUNAR  APENNINES. 

The  diagonal  range  is  that  of  the  Apennines ;  the  great  mountain  ring  in  the  lower'patt 
of  the  photo  is  "  Archimedes." 


ON   THE   MOON  107 

conclusion  does  not  hold  good  as  matters  actually 
are,  for  the  stone  on  the  Moon  is  much  nearer 
its  attracting  centre.  The  figure  just  given  is  there- 
fore far  from  expressing  the  reality,  and  making  all 
necessary  calculations,  as  we  know  the  radius  (or 
semi-diameter)  of  the  Moon,  we  find  that  the  force 
of  gravity,  or  weight,  on  our  satellite  is  only 
one-sixth  of  the  average  of  that  same  force  at  the 
surface  of  the  Earth. 

And  there  is  another  consequence — if  you  weigh 
here  on  the  Moon  what  would  be  60  pounds  with 
us,  a  spring  balance  would  indicate  only  a  weight  of 
10  pounds,  and  as  your  muscular  force  remains 
the  same  as  ever,  you  now  understand  how  here 
you  can  succeed  in  easily  lifting  an  enormous  block 
of  stone. 

In  the  same  way,  before  jumping  over  an  ob- 
stacle, or  leaping  across  a  mass  of  sloping  debris 
or  an  open  crevasse,  you  will  do  well  to  be  careful, 
and  to  remind  yourself  that  an  effort  which  would 
enable  you  "  in  your  own  country "  to  make  a 
jump  of  6  feet  would  carry  you  to  a  distance  of 
36  feet  on  the  surface  of  the  Moon. 

But  if  we  take  certain  precautions  this  diminution 
of  jweight  is  just  what  will  give  us  an  unexpected 


108  A   DAY   IN    THE   MOON 

means  of  reaching  without  difficulty  the  base  of  this 
tremendous  declivity,  and  rapidly  making  our  way 
to  the  outlying  hill-buttresses  of  the  great  chain 
of  the  lunar  Apennines. 

Isolated  peaks  rearing  their  crests  above  a  vast 
desert,  numbers  of  great  tumuli  in  the  summits  of 
which  open  yawning  craters  whose  depth  the  eye 
cannot  fathom,  low  hills,  parallel  furrows,  some 
basin-shaped  hollows,  and  here  and  there  enormous 
crevasses — such  is  the  appearance  of  the  wide  tract 
that  we  traverse  to  the  north  of  Copernicus  in  order 
to  reach  the  great  "  Sea  of  Rains "  (the  Mare 
Imbrmni]. 

We  might  thus  make  a  march  of  hundreds  of 
miles  always  in  the  midst  of  this  desert-like  steppe 
with  its  overheated  surface  burned  up  by  the  blaze 
of  an  unendurably  tropic  sun. 

At  the  lunar  noon — that  is  to  say,  when  the  Sun 
has  completed  half  its  course  across  the  sky — the 
ground  will  be  heated  to  such  a  degree  that  it 
would  immediately  roast  any  organic  substance 
placed  upon  its  surface.  The  temperature  would 
be  above  212  degrees,  and  during  the  long  lunar 
night  of  about  two  weeks  a  gas  thermometer  would 
indicate  a  cold  of  some  300  degrees  below  zero. 


REGION  OF  THE  "  MARE  SERENITATIS." 

The  great  plain  is  the  so-called  "  Sea  of  Serenity."  The  isolated  crater  in 
its  upper  part  is  "  Bessel."  The  large  crater  near  the  end  of  the  range  forming 
its  upper  boundary  is  "  Plinius." 

108] 


ON  THE   MOON  109 

What  plants,  what  animals  could  survive  such 
extremes  and  such  variations  of  temperature  ? 

But  already  the  Apennines  are  in  sight.  For 
400  miles  this  mountain  range,  the  most  beautiful 
in  our  satellite,  will  close  in  our  horizon  to  the 
eastward. 

It  has,  however,  no  resemblance  to  the  mountain 
masses  of  our  own  Alps.  Here  we  have  a  titanic 
piling  up  of  rocky  material,  heaped  together  with 
a  breadth  that  in  some  places  is  as  much  as  160 
miles,  especially  where  the  chain  appproaches  the 
"  Sea  of  Vapours." 

From  this  shapeless  mass  there  rise  up  slender 
peaks  of  which  you  can  see  the  long  shadows  on 
our  right,  forests  of  rocky  steeples,  columns, 
minarets,  gigantic  obelisks,  crowding  together  their 
impossible-looking  shapes  to  form  a  panorama  that 
seems  something  unreal,  masses  of  dazzling  blue 
on  a  black  background  all  spangled  with  stars. 

Behind  us  the  great  mountain  ring  of  Eratos- 
thenes stands  out  strongly  from  the  monotonous 
plain  that  marks  the  beginning  of  the  "  Sea  of 
Rains." 

Let  us  press  on  continually  to  the  northwards. 
We  salute  as  we  pass  it  by  the  square-shaped  mass 


i  io  A   DAY   IN   THE   MOON 

of  the  Wolf  Mountains,  of  which  the  loftiest 
summit  reaches  a  height  of  12,000  feet,  and  Mount 
Huyghens  with  its  tall  peak,  whose  summit  goes  up 
to  an  altitude  of  18,000  feet. 

Now  in  front  of  us  and  a  little  to  our  left, 
an  enormous  mass  rises — the  mountain  ring  of 
Archimedes,  the  interior  diameter  of  which  is  not 
less  than  50  miles.  We  are  now  in  the  "  Marsh 
of  Fogs."  Cast  a  glance  as  we  pass  by  at  Thea- 
tetus,  the  little  volcano  near  which  certain 
astronomers  think  they  have  made  out  a  trail  of 
smoke.  We  have  now  reached  the  first  buttresses 
of  the  lunar  Alps.  Once  more  we  see  great  peaks 
rising  before  us,  but  they  are  less  numerous  than 
those  in  the  Apennine  chain,  where  selenographers 
have  counted  up  more  than  3,000. 

Here  the  eye  distinguishes  only  some  hundreds, 
of  which  the  most  remarkable  is  "  Mont  Blanc,'* 
with  its  height  of  nearly  12,000  feet. 

At  the  base  of  its  precipitous  sides  a  wide  valley 
opens  out,  a  fantastic  gap  stretching  away  in  a 
straight  line  as  far  as  the  eye  can  reach,  a  giant 
furrow  that  underground  forces  have  formed  in 
the  midst  of  this  impenetrable  scene  of  mountain 
chaos. 


ON  THE   MOON  in 

Not  far  from  here  rises  the  huge  circle  of  Plato, 
a  vast  arena  60  miles  across. 

But  the  hours  are  going  by,  and  the  Sun  is 
inclining  towards  the  west.  Let  us  hasten  our 
steps  towards  the  "  Sea  of  Serenity,"  and  continue 
our  excursion  so  as  to  reach  the  southern  part  of 
the  Moon. 

We  are  now  nearing  Linnee,  a  small  crater  which 
for  years  has  been  raising  amongst  astronomers  the 
question  of  changes  in  the  Moon. 

Linnee  was  very  closely  observed  by  earlier 
selenographers.  Now  modern  descriptions  do  not 
at  all  correspond  to  those  given  by  Lohrmann, 
Schroeter,  Huggins,  and  several  others. 

It  would  seem  that  in  the  first  half  of  the  nine- 
teenth century  important  changes  took  place  in  the 
appearance  of  this  curious  object,  and  that  in  1866 
its  interior  was  filled  up  with  some  kind  of  white 
matter,  very  likely  lava. 

The  two  little  craters  of  Messier  show  also  very 
curious  changes  of  appearance  ;  now  they  are  visible, 
now  they  are  hidden  by  a  screen  that  looks  like 
smoke. 

We  may  also  take  note  of  the  observations  of 
MM.  Charbonneaux  and  Millochau,  who  remarked 


ii2  A   DAY   IN   THE   MOON 

similar  appearances — whitish  patches  some  4  miles 
long,  showing  themselves  over  a  little  crater  situated 
near  Theatetus,  which  we  remarked  as  we  passed 
by  it. 

The  study  of  all  these  facts,  and  of  a  number  of 
others  which  have  not  been  so  fully  investigated, 
raises  therefore  once  more  the  problem  of  the 
internal  activity  of  a  central  fire  in  our  satellite. 
It  is  very  difficult  to  admit  the  possibility  of  the 
presence  in  the  Moon  of  appearances  due  to  any 
vegetation  surviving  even  on  the  low-lying  plains, 
but  we  have  yet  to  find  some  explanation  for  certain 
changes  of  colour  that  recur  with  each  lunation, 
and  for  a  number  of  variations  that  fit  in  very 
well  with  the  supposition  that  internal  forces  are 
still  reshaping  the  topography  of  the  Moon's 
surface. 

Besides,  the  geology  of  this  land  so  near  our  own 
is  well  calculated  to  puzzle  even  the  most  learned. 
The  surface  crust  of  our  satellite  has  been  subjected 
to  the  action  of  powerful  forces  that  have  no 
analogy  with  those  which  appear  to  have  determined 
the  surface  features  of  our  Earth. 

It  is  probable  that  at  the  outset — that  is  to  say, 
at  the  period  when  the  Moon  was  in  a  viscous 


o 


W 


ON  THE   MOON  113 

state — the  gases  imprisoned  in  the  interior  of  its 
mass  raised  here  and  there  enormous  domes,  a  kind 
of  gigantic  bubble,  thus  leading  up  to  the  falling  in 
of  the  surface  on  a  vast  scale  and  in  circular  or 
elliptic  shapes. 

This  would  be  the  origin  of  such  great  depres- 
sions as  the  "  Sea  of  Crises,"  the  "  Sea  of  Serenity," 
the  "  Sea  of  Rains,"  etc.  All  these  are  in  fact 
bounded  by  mountain  masses,  of  which  the  steepest 
side  is  always  turned  to  the  part  that  has  fallen  in. 

Later  on,  as  the  crust  gradually  became  thicker, 
these  swellings  of  the  surface  were  localised  within 
narrower  limits ;  the  consequent  collapse  of  the 
surface  resulting  in  the  formation  of  mountain  rings 
like  Tycho,  Ptolemy,  Theophilus,  etc.  .  .  .  The 
presence  of  central  mountains  in  these  rings  is  also 
fairly  well  explained  by  this  theory — for  want  of 
room  certain  parts  of  the  falling  dome  were  forced 
to  pile  themselves  up  one  on  the  other. 

In  some  cases  the  rise  of  floods  of  lava  has  more 
or  less  filled  up  the  inner  arena,  and  overflowed 
in  metallic  streams  through  gaps  in  the  encircling 
walls. 

Finally,  when   the  outer  crust  could   no   longer, 
on  account  of  its  want  of  elasticity,  bend  to  the 
8 


1 14  A   DAY   IN   THE    MOON 

upward  force  of  the  interior  gases,  the  envelope 
cracked  and  split  around  the  points  of  pressure, 
and  we  might  thus  account  for  those  broad  rays 
that  seem  to  radiate  from  certain  mountain  rings, 
such  as  those  of  Tycho,  Kepler,  and  Copernicus. 
Sometimes  the  breaks  resulting  from  this  upward 
pressure  from  within  have  formed  long  yawning 
chasms,  as  in  the  ineighbourhood  of  Triesnecker  or 
Hyginus  ;  sometimes  they  have  been  filled  up  by 
metallic  lavas,  as  in  the  case  of  the  rays  around 
Tycho,  where  we  see  them  glittering  more  and 
more  brightly  as  the  Sun  rises  higher  above  the 
horizon. 

The  southern  part  of  the  Moon — that  which  we 
see  at  the  top  in  an  astronomical  telescope  which 
reverses  the  object — is  not  at  all  like  the  regions 
we  have  just  visited. 

To  get  an  idea  of  it,  let  us  rise  above  the  surface 
of  the  Moon  and  continue  our  journey  so  as  to 
have  a  bird's-eye  view — from  an  aeroplane,  if  you 
like. 

Your  first  impression  at  the  sight  of  this  wild 
landscape  will  make  you  think  of  a  huge  volcanic 
region,  but  as  you  look  more  closely  you  will 
soon  find  out  your  mistake. 


O    X 
."=    H 

i  o 


ON   THE   MOON  115 

The  real  lunar  volcanoes  are  hardly  visible  with 
our  most  powerful  telescopes. 

The  great  circles  displayed  before  your  eyes  are 
all  vast  plains  surrounded  by  mountain  ramparts. 

First  of  all  there  are  Hipparchus  and  Ptolemy, 
measuring  about  125  miles  in  diameter.  Their 
inner  arena  is  full  of  eruptive  mouths  that  we 
cannot  count.  Broad  valleys  open  to  the  south  of 
Ptolemy,  towards  Alphonso  and  Arzachel,  and  there 
is  nothing  on  earth  that  can  give  us  an  idea  of 
such  a  confused  mountain  upheaval.  Peaks  of 
6,500,  10,000,  13,000  feet  overhang  yawning 
hollows  12  miles  across  ;  volcanic  cones  have  risen 
by  hundreds  on  the  bare  abrupt  slopes  ;  then  over 
vast  extents  of  ground  the  crust  has  fallen,  pro- 
ducing gigantic  cracks  as  in  that  region  of  the 
"  Sea  of  Mists,"  1  where  the  arena  of  an  old  mountain 
ring  is  split  in  two. 

A  good  half  of  it  has  sunk  down,  and  the  two 
edges  of  the  "fault"  have  actually  a  difference  of 
level  amounting  to  2,300  or  2,600  feet ;  this  is 
the  "Straight  Range"  to  be  seen  near  "Birt," 
and  which  in  certain  lights  takes  the  form  of  a 
sword. 

1  The  Mare  Vaporum. 


n6  A  DAY   IN  THE   MOON 

Farther  south  the  elevations  become  still  higher 
in  the  direction  of  Tycho  and  Maginus. 

Then  there  is  Clavius,  with  its  boldly  shaped 
rampart,  a  deep  cavity  overhung  by  mountains 
more  than  16,000  feet  high,  with  a  vast  arena  142 
miles  in  diameter. 

Behind  us  Maurolycus  and  Stoefler,  already 
shrouded  in  night,  show  only  the  shining  tips  of 
their  fantastic  summits. 

But  the  south  pole  of  the  Moon  has  a  greater 
surprise  in  store  for  us.  Against  the  dark  sky 
there  stands  out  a  gigantic  mountain  chain,  higher 
in  proportion  than  our  Himalayas,  for  the  Leibnitz 
Mountains  probably  rise  above  the  level  of  25,000 
feet.  Beside  these  lunar  giants  the  Doerfel  Moun- 
tains show  up  their  imposing  masses,  amongst  which 
Schroeter  and  Madler  have  measured  summits 
26,000  feet  high. 

Here  the  eye  of  the  astronomer  can  go  no 
farther.  The  Moon,  as  we  have  seen,  always 
presents  the  same  side  to  the  Earth.  What  kind 
is  the  other  side  ?  It  is  a  mystery.  And  no  human 
being  will  ever  be  able  to  solve  it.  Certain  learned 
men  of  the  past  tried  to  make  out  that,  as  a  result 
of  the  Earth's  attraction,  the  Moon  must  have 


55 
O  =. 

O  *i 


W  s 
K  o 
H  :S 


H    M 

1! 


H  O 

«  S 

5.  <H 

o  „ 


- 


ON   THE   MOON  117 

taken  an  irregular  form,  that  of  an  egg,  of  which 
the  longer  end  is  turned  towards  us. 

On  the  other  hand,  it  has  been  an  easy  matter 
for  us  to  assure  ourselves  of  the  absence  of  any 
atmosphere  on  the  visible  part  of  the  Moon.  We 
know  that  every  ray  of  light  is  bent  by  refraction 
in  passing  through  the  layers  of  our  atmosphere, 
and  this  is  why  the  Sun  is  visible  a  little  before 
its  time  of  rising  and  a  little  after  its  setting. 

In  the  same  way,  in  the  case  of  an  "  occultation," 
when  the  Moon  passes  between  us  and  a  star,  if 
there  were  refraction — and  therefore  a  lunar  atmo- 
sphere— the  star  would  not  disappear  at  the  exact 
moment  given  by  calculation,  and  the  time  it  was 
hidden  from  us  would  be  shortened. 

Well,  on  this  point  observation  has  never  been 
in  disagreement  with  theory,  and  so  the  partisans 
of  a  lunar  atmosphere,  obliged  to  abandon  this 
point,  have  not  quite  given  up  the  game  as  lost. 
"  If  the  Moon,"  they  say,  "  is  more  elongated  on 
our  side  of  it,  the  opposite  side  is  nearer  the 
centre,  therefore  lower,  and  it  is  precisely  in  that 
region  the  air  has  accumulated." 

Unfortunately  for  them,  measurements  taken  from 
contour  lines  drawn  for  the  Moon  by  Dr.  Franz 


n8  A   DAY   IN   THE    MOON 

have  not  confirmed  this  way  of  looking  at  the 
matter.  The  Moon  is  indeed  a  practically  spherical 
body.  The  most  one  can  grant  is  that  subsidences 
of  the  crust — which,  however,  are  of  no  great 
importance — have  taken  place  there  as  on  the  Earth. 
These  are  the  result  of  a  law  which  we  shall  study 
in  a  future  volume — a  law  that  points  to  the 
opposite  side  of  the  Moon  roughly  resembling  the 
drawing  we  give  here. 

However,  it  is  not  quite  strictly  correct  to  say 
that  we  can  see  only  one  side  of  the  Moon. 

Our  satellite  indeed  completes  its  movement  of 
rotation  and  revolution  in  the  same  time,  but  the 
orbit  it  follows  is  an  ellipse. 

When  the  Moon  has  gone  through  a  quarter  of 
its  orbital  movement  it  has  revolved  a  little  more 
than  a  quarter  on  its  own  axis.  An  astronomer 
on  the  Earth  therefore  sees  in  each  lunation  a 
border  or  lateral  segment  that  he  would  never 
have  a  sight  of  if  the  Moon  described  an  exact 
circle  in  its  movement  round  the  Earth. 

Thanks  to  this  phenomenon  of  libration  (as  it  is 
called),  the  Moon  seems  to  possess  a  sort  of 
swaying  movement,  in  consequence  of  which  we 
know  a  little  more  than  the  half  of  its  surface. 


H     jj 

X   2 


1 11 

W        M    fl 


S  1§ 

W   •*- ja 
K   s-ti 


o 

£    ? 
O    '.2 

Si 

s  - 
*  s 

o    ° 


H     .« 

^     I 

§1 


ON   THE   MOON  119 

Similar  phenomena,  due  to  other  causes,  allow  us 
to  get  sight  of  a  narrow  border  at  the  north  and 
south.  Well,  all  we  thus  get  a  glimpse  of  points 
to  the  supposition  that  the  other  side  of  the 
Moon  has  a  similar  constitution  to  that  which 
we  see. 

But  it  is  time  to  return  to  the  Earth,  which 
we  can  see  all  this  time  high  in  the  sky.  The 
Sun  is  already  setting,  and  its  last  blue  margin  will 
soon  disappear  below  the  horizon.  The  lengthening 
shadows  already  warn  us  of  the  approach  of  the 
lunar  night.  The  cold  begins  to  assail  us.  Let 
us  fly  from  those  endless  plains,  those  monstrous 
peaks,  those  countries  of  death  and  desolation,  those 
silent  landscapes,  those  frightful  solitudes,  those 
black  tomb-like  chasms,  those  granite  precipices, 
those  awful  summits  where  no  gust  of  wind  any 
longer  goes  by,  those  slender  spires  of  rock  whose 
balance  there  is  no  longer  anything  to  alter,  those 
deserts  that  life  has  quitted  for  ever  ;  let  us  fly 
from  this  region  of  eternal  silence,  with  its 
apocalyptic  visions  and  its  sepulchres  that  the  angel 
of  death  has  closed  with  his  icy  wings. 


VIII 

THE    MOON,    THE    TIDES,    AND    THE 
CHANGES   OF  THE   WEATHER 

WE  have  seen  in  the  preceding  chapters  that  the 
Moon  attracts  the  Earth,  just  as  the  latter  exerts 
an  attraction  on  its  satellite.  The  intensity  is 
obviously  not  the  same,  seeing  that  their  masses 
are  in  the  proportion  of  I  to  81-5. 

This  attraction  of  the  Moon  influences  also  terres- 
trial objects,  and  this  is  easy  to  understand.  If  you 
strew  iron  filings  on  the  surface  of  a  magnet,  the 
particles  will  attach  themselves  to  the  magnetised 
metal ;  and  if  you  bring  another  powerful  magnet 
near  it,  you  understand  quite  well  that  the  action 
of  this  second  magnet  has  the  effect  of  diminishing 
the  attraction  of  the  first  for  the  filings. 

When,  for  instance,  the  Moon  passes  between 
the  Sun  and  the  Earth,  it  must  add  its  effect  to 
that  of  the  Sun,  and  terrestrial  objects  must  be 
attracted  to  some  small  extent  by  the  mass  of  the 


120 


MOON,   TIDES,   AND   WEATHER     121 

two  globes,  but  above  all  by  that  of  the  Moon, 
which  is  much  the  nearer. 

Very  delicate  observations  are  required  to  measure 
this  diminution  in  the  intensity  of  gravitation  or 
weight,  but  nevertheless  the  phenomenon  takes 
forms  that  render  measurement  easy  when  we  con- 
sider it  in  the  total  effect  of  the  action  it  exercises 
on  the  oceans  that  envelop  the  Earth.  It  causes 
a  periodical  rise  in  them,  which  we  know  by  the 
name  of  the  tide. 

Every  time,  in  fact,  that  the  Moon  passes  over 
a  region  of  our  globe,  the  particles  of  water,  being 
less  attracted  by  the  Earth,  are  raised  towards  the 
Moon,  the  whole  mass  moving  towards  the  precise 
point  where  the  attraction  of  the  Moon  is  strongest, 
and  the  phenomenon  changing  its  place  according 
to  the  course  of  our  satellite  and  its  progress  in 
the  heavens. 

At  first  sight  it  is  more  difficult  to  understand 
why  this  kind  of  swelling  of  the  ocean,  this  rising 
up  of  the  waters  under  the  Moon,  should  take 
place  also  in  the  opposite  region  of  the  Earth — 
that  is  to  say,  at  the  Antipodes.  And  nevertheless, 
theoretically  it  must  be  so. 

At  the  antipodes  of  the  place  at  which  the  Moon 


122  A   DAY   IN   THE   MOON 

is  on  the  meridian,  all  the  particles  of  the  ocean 
that  are  situated  farther  from  our  satellite  than  the 
centre  of  the  Earth  are  subjected  to  a  weaker 
attraction.  They  have  thus  less  tendency  to  draw 
nearer  to  the  Moon,  and  consequently  they  rather 
tend  to  a  delay  in  moving  towards  it  ;  there  should 
therefore  be  a  high  tide. 

If  this  explanation  seems  to  you  difficult  to 
grasp,  take  at  least  this  much  of  it  :  Every  molecule 
of  water  situated  on  the  farther  side  of  the  Earth 
as  regards  the  Moon,  by  this  fact  is  subject  to  a 
minimum  attraction  on  the  part  of  the  Moon  ; 
therefore,  on  the  part  of  the  Earth  farthest  from 
the  Moon  the  liquid  element  is  less  heavy  than  in 
the  regions  at  both  sides  of  it.  Now,  physical 
science  demonstrates  that  if  one  puts  liquids  of 
different  density  into  the  two  branches  of  a  tube 
bent  into  the  form  of  the  letter  U,  in  order  to  be 
at  equilibrium  the  less  heavy  liquid  must  stand  at  a 
higher  level.  And  this  is  precisely  what  happens 
in  the  ocean  on  the  opposite  side  from  the 
Moon. 

This  simple  explanation,  however,  was  not  known 
to  the  ancients.  It  would,  indeed,  have  been  enough 
for  them  to  have  remarked  that  the  phenomenon 


MOON,   TIDES,  AND   WEATHER     123 

of  the  tides  has  an  evident  connection  with  the 
passage  of  the  Moon  across  the  meridian,  for  the 
tide,  like  the  Moon  in  the  sky,  is  about  three- 
quarters  of  an  hour  later  each  day. 

It  is,  however,  true  that,  though  there  are  two 
periods  of  ebb  and  flow  in  a  day,  the  moment 
of  high  water  does  not  actually  occur  till  after  the 
passage  of  the  Moon  across  the  meridian  of  the 
place,  and  one  must  take  into  account  the  position 
of  the  points  of  observation  and  the  configuration 
of  the  coast. 

It  was  Kepler  who  first  suspected  the  true  cause 
of  the  tide  and  attributed  it  to  the  action  of  the 
Moon  ;  but  it  was  the  fate  of  this  remarkable 
genius  that  his  theories  had  no  chance  of  success 
in  his  lifetime. 

In  1 63  i  one  of  his  contemporaries  in  connection 
with  this  very  subject  called  him  a  visionary,  and 
as  his  opponent  was  a  scientific  man — I  was  going 
to  say  an  official  one — poor  Kepler  could  only  bow 
his  head. 

And  all  the  same,  he  who  thus  took  to  task 
the  illustrious  Kepler  was  not  exactly  a  partisan  of 
Aristotelian  philosophy  ;  he  was  always  claiming 
for  himself  the  right  of  freedom  of  thought,  and 


124  A   DAY   IN   THE   MOON 

if  I  did  not  tell  you  his  name  you  would  be  quite 
unable  to  guess  it. 

This  learned  man  had  already  shown  himself 
much  the  weaker  of  the  two  in  a  discussion  on 
physics  with  Torricelli,  and  his  name  was  .  .  . 
Galileo ! 

As  the  Moon  has  an  action  upon  the  oceans — 
that  is  to  say,  on  the  liquid  envelope  of  the  globe 
— one  might  expect  a  -priori  that  in  studying  the 
general  laws  of  our  atmosphere  we  would  find  in 
it  a  tide  somewhat  similar  to  that  to  which  the 
liquid  mass  is  subject. 

It  is  an  interesting  problem,  because  it  might 
lead  us  to  practical  results  from  the  meteorological 
point  of  view. 

With  the  idea  that  a  tide  in  the  atmosphere  could 
not  take  place  without  causing  widespread  dis- 
turbances, more  than  one  builder  of  theories  has 
already  suggested  a  possible  relation  between  the 
phases  of  the  Moon  and  the  changes  of  the 
weather. 

Simple  in  appearance  as  the  problem  is,  it  is 
nevertheless  one  of  the  most  complex  that  men  of 
science  have  had  to  solve.  So  they  have  attacked 
it  from  several  different  sides  at  once. 


Photo  taken  at  the  Paris  Observatory. 

REGION  OF  THE 


MARE  VAPORUM." 


At  the  base  of  the  photograph  is  the  Mare  Vaporum  ;  above  this  is  seen 
Triesnecker  with  its  long  clefts  or  crevasses.  The  great  mountain  ring  at  the  top 
and  to  the  right  is  Ptolemy,  117  miles  in  diameter. 

124] 


MOON,   TIDES,   AND  WEATHER     125 

In  some  countries  experience  has  shown  that 
there  is  more  rain  during  the  time  the  Moon  is 
increasing  than  when  it  is  waning.  This  is  clearly 
the  case  in  the  north  of  France  and  Germany,  and 
our  meteorological  records  supply  good  evidence  of 
this  fact. 

However,  we  must  not  exaggerate  the  importance 
of  the  relation  between  the  number  of  rainy  days 
of  the  first  period  and  those  of  the  second  ;  the 
difference  is  extremely  slight. 

But  in  the  south  of  France  this  law  does  not 
hold  good  :  it  is  even  reversed. 

And  besides,  theoretically  it  is  easy  to  fix  by 
calculation  the  amount  of  this  lunar  tide  of  the 
atmosphere.  It  works  out  in  tenths  of  millimetres 
at  its  maximum,  and  thus  comes  within  the  range 
of  mere  errors  of  observation  ;  that  is  to  say,  it 
does  not  appreciably  affect  our  barometers. 

The  explanation  is  perhaps  to  be  sought  elsewhere. 

We  know  that  the  variations  of  the  barometer, 
especially  notable  falls  of  it,  are  not  essentially 
connected  with  changes  of  weather. 

France  and  Western  Europe  are  in  a  somewhat 
exceptional  position  for  profiting  by  the  indications 
of  the  barometer. 


126  A    DAY   IN   THE    MOON 

The  southern  regions  are  much  less  subject  to 
the  influences  of  the  Gulf  Stream  than  those  of 
the  north,  and  conditions  such  as  bring  rainy 
weather  in  one  place  do  not  produce  the  same 
effect  in  other  districts. 

Is  there  any  meteorologist  of  to-day  who  can 
flatter  himself  that  he  knows  thoroughly  the 
conditions  that  bring  rain  ? 

It  may  very  well  be  that  the  Moon  by  its 
presence  above  the  horizon  has  some  connection 
with  rainfall  through  chemical  action,  electric  action, 
or  the  effect  of  ionisation,  and  through  slight 
mechanical  action. 

It  is  therefore  most  prudent  to  hesitate  before 
making  any  pronouncement,  and  it  is,  above  all, 
our  duty  not  to  deny  the  facts  under  the  pretext 
that  we  cannot  see  any  explanation  for  them. 

Here,  as  elsewhere,  it  may  be  that  popular 
belief  knows  better  than  the  men  of  science. 

Moveover,  there  is  something  to  be  said  for 
the  truth  of  the  theory  from  another  point  of  view. 
In  recent  years  mathematicians  have  approached 
the  question  by  another  way,  that  seems  likely  to 
give  more  results. 

We  have  already  noted  that    the    Moon    is    not 


MOON,   TIDES,  AND   WEATHER     127 

always  at  the  same  distance  from  the  equator  of 
the  heavens.  Its  movements,  considered  in  relation 
with  the  plane  of  the  elliptic,  to  which  the  Earth's 
axis  is  inclined,  give  rise  to  a  phenomenon  that 
everybody  can  observe  for  himself. 

There  are  times  when  it  passes  the  meridian 
at  a  great  height  in  the  sky,  tracing  a  very  large 
arc  of  a  circle  above  the  horizon.  At  others,  on 
the  contrary,  it  remains  confined  to  the  regions 
towards  the  south,  does  not  rise  high,  and  sends 
us  its  rays  very  obliquely. 

So  the  depth  of  atmosphere  on  which  it  exerts 
its  action  is  continually  varying.  Our  satellite  thus 
produces  displacements  of  the  air,  a  kind  of 
enormous  swelling  outwards,  that  passes  slowly 
from  the  tropical  regions  to  higher  latitudes. 

This  is  what  calculation  proves.  What  has 
observation  to  tell  us  on  the  subject  ? 

Exactly  the  same  thing.  The  limit  of  the  region 
of  the  trade  winds  is  subject  to  a  periodical  move- 
ment backwards  and  forwards  corresponding  to 
the  declination  of  the  Moon.  This  movement, 
or  rather  this  swaying  of  the  zones  of  high  and 
low  pressures,  which  is  radically  linked  with 
a  unique  phenomenon,  may  therefore  bring  fine 


128  A   DAY   IN   THE    MOON 

weather  and  rain  simultaneously  but  in  different 
regions. 

The  combination  of  this  effect  with  the  Full 
Moon  or  the  New  Moon  is  perhaps  in  more  than 
one  instance  an  additional  element  in  modifying  the 
weather,  so  that,  all  things  considered,  I  do  not 
despair  of  seeing  men  of  science  gradually  coming  to 
a  proof  of  what  all  the  world  admitted  long  since, 
namely,  that  our  satellite  really  counts  for  something 
in  certain  atmospheric  changes. 

But  we  must  take  care  not  to  exaggerate  or  push 
things  to  extremes.  The  intermediate  phases  be- 
tween Full  Moon  and  New  Moon  do  not  seem  to 
be  so  chargeable  with  the  bad  results  popularly  attri- 
buted to  them. 

"But,"  you  say,  "what  about  the  'Rust 
Moon  '  ? " 

Patience  !     We  are  coming  to  that. 

First  of  all,  do  you  know  the  meaning  of  the 
word  ?  and  at  what  period  the  Rust  Moon 
appears  ? l 

Towards  the  end  of  April,  or  rather  during  the 

1  The  popular  belief  which  the  author  here  discusses  is  common 
among  the  French  peasantry,  but  does  not  seem  to  be  current  among 
country  folk  in  England. — Translator's  Note. 


MOON,   TIDES,   AND   WEATHER     129 

month  of  May,  when  the  temperature  of  the  day 
begins  to  increase  perceptibly,  and  thus  conditions 
are  favourable  for  the  rising  of  sap  in  plants,  a 
somewhat  curious  phenomenon  occurs  every  year. 

Put  out  a  minimum  thermometer  a  little  above 
the  ground,  and  you  will  find  that  even  during 
nights  in  which  the  indicator  has  not  gone  down 
to  freezing-point  some  plants  have  been  frost-bitten, 
and  the  affected  buds  are  a  sort  of  rust  colour. 
Now,  this  occurs  always  under  a  clear,  cloudless  sky. 
If  the  Moon  is  above  the  horizon,  it  is  of  course 
quite  visible  ;  hence  the  accusation  brought  against 
it  by  the  peasants  of  "  rusting  "  the  plants. 

The  "  Rust  Moon  "  has  been  known  from  time 
immemorial.  Market  gardeners  and  vine  growers 
are  afraid  of  it,  and  they  attribute  its  ravages  to  a 
special  cold-producing  power  in  the  rays  of  our 
satellite.  Let  us  see  if  there  is  any  basis  for  this 
accusation.  In  any  case  the  "  Rust  Moon "  has 
been  officially  known  to  men  of  science  only  for 
a  century,  as  is  shown  by  this  story  related  by 
Arago : 

"  *  1  am  pleased  to  see  you  gathered  around  me,' 
said  Louis  XVIII  one  day  to  the  members  of  a 
deputation  of  the  Bureau  des  Longitudes,  who  had 
9 


130  A   DAY   IN   THE   MOON 

come  to  present  to  him  their  Almanac  and  Annual, 
4  for  you  will  clearly  explain  to  me  what  is  the  Rust 
Moon  and  how  it  acts  upon  the  crops.' 

"  Laplace,  to  whom  these  words  were  specially 
addressed,  seemed  dumbfounded  :  though  he  had 
written  so  much  about  the  Moon,  he  had  in  fact 
never  dreamed  of  such  a  thing  as  the  Rust  Moon. 
He  appealed  with  a  look  to  all  his  colleagues,  but 
as  no  one  seemed  inclined  to  speak,  he  decided  to 
reply  himself : 

"  '  Sire,  the  Rust  Moon  has  no  place  in  astro- 
nomical theory.  We  are  not  in  a  position,  therefore, 
to  satisfy  the  curiosity  of  your  Majesty.' 

"  That  evening,  when  at  the  card-table,  the  King 
made  very  merry  over  the  embarrassment  into  which 
he  had  thrown  his  Bureau  of  Longitudes.  Laplace 
heard  of  it,  and  went  to  see  Arago  at  the  Ob- 
servatory in  order  to  ask  him  if  he  could  throw  any 
light  on  this  famous  '  Rust  Moon '  that  had  given 
rise  to  such  a  disagreeable  incident.  Arago  knew 
no  more  about  it  than  Laplace,  but  he  promised  the 
illustrious  astronomer  that  he  would  make  inquiries 
of  the  gardeners  of  the  Jardin  des  Plantes  and  other 
horticulturists. 

"  As  the  result  of  his  investigation,  Arago  settled 


From  a  drawing  by  the  Abbe  Moreus. 

INTERIOR  OF  A  LUNAR  VOLCANO. 


130] 


MOON,   TIDES,   AND   WEATHER     131 

that  henceforth  the  '  Rust  Moon  '  would  be  taken  to 
be  that  which  beginning  in  April  reaches  the  Full 
either  at  the  end  of  that  month  or  oftener  in  the 
course  of  the  month  of  May." 

I  do  not  know  if  the  definition  is  perfect.  It  has 
often  given  rise  to  excited  discussions,  which  how- 
ever seem  to  me  very  puerile. 

The  gardeners  settle  it  each  year  in  their  own 
way.  Sometimes  their  plants  are  touched  by  the 
frost,  sometimes  they  don't  do  very  badly,  and  the 
"  Rust  Moon  "  does  not  always  "  rust "  them.  But 
however  this  may  be,  we  have  here  the  popular 
account  of  a  fact  that  we  may  look  into  more  closely. 

Agriculturists,  as  we  have  said,  assert  that  at 
night  with  a  clear  sky  leaves  and  buds  exposed  to 
the  moonlight  are  "  rusted,"  in  other  words  are 
frost-bitten,  although  the  thermometer  exposed  to 
the  air  remains  several  degrees  above  freezing-point. 
On  the  other  hand,  if,  as  the  result  of  the  presence 
of  clouds  in  the  sky,  the  rays  of  the  Moon  do 
not  reach  the  plants,  these  effects  are  not  observed, 
although  the  general  temperature  of  the  air  remains 
the  same. 

It  would  seem  then,  at  first  sight,  that  the  lunar 
rays  are  the  cause  of  this  chilling. 


132  A   DAY   IN   THE   MOON 

Nevertheless,  if  at  the  time  of  New  Moon,  when 
our  satellite  is  not  above  the  horizon,  the  sky  clears, 
you  will  find  that  the  young  shoots,  especially  those 
of  the  vine,  freeze  and  "  rust  "  just  the  same. 

The  Moon  has  therefore  nothing  to  do  with  the 
matter,  and  the  explanation  of  it  must  be  looked  for 
elsewhere. 

The  cold  of  the  night  was  specially  studied  long 
ago  by  Wilson,  and  here  is  what  that  physicist 
observed  in  1783  : 

After  having  placed  a  thermometer  on  the  snow 
and  noted  that  it  indicated  about  22°  below  zero, 
while  the  temperature  shown  by  another  4  feet 
from  the  ground  was— 14°,  he  saw  the  lower  ther- 
mometer suddenly  rise  some  8°  as  clouds  came 
over  the  sky. 

When  the  night  is  fine  and  clear,  therefore, 
bodies  lose  their  heat  by  the  simple  process  of 
radiation.  The  presence  of  a  screen  or  cloud,  or 
a  covering  of  canvas  or  of  straw,  slight  though  it 
may  be,  at  once  neutralises  this  effect. 

All  our  readers  can  easily  repeat  Wilson's  ex- 
periments. They  will  find  that  in  still,  cloudless 
nights  the  grass  has  always  a  lower  temperature 
than  the  air  six  feet  above  it.  We  must  not,  there- 


MOON,   TIDES,   AND  WEATHER     133 

fore,  judge  of  the  cold  that  affects  a  plant  during 
the  night  merely  by  the  readings  of  a  thermometer 
hanging  in  the  air. 

This  phenomenon  is  perfectly  well  known,  and 
has  been  taken  advantage  of  from  time  imme- 
morial— in  India,  for  instance — for  making  ice. 
Shallow  vessels  filled  with  water  are  arranged  in  an 
excavation  filled  with  maize  straw.  A  bank  of 
earth  runs  round  it  to  keep  the  cooled  air  from 
disturbance.  When  the  sky  is  clear  and  the  air 
calm  without  too  much  humidity,  and  the  tempera- 
ture falls  below  50°,  the  water  freezes,  even  when 
a  thermometer  laid  on  the  straw  indicates  40°. 
One  hears  of  ice-makers  who  employ  in  this  way 
hundreds  of  workmen,  and  the  process  was  used 
for  the  same  purpose  by  the  physicist  Wells,  who 
repeated  the  experiment  in  England  during  the 
summer. 

But  to  succeed  one  must  have  a  clear  night ;  in 
cloudy  weather  there  is  no  radiation,  and  the  dif- 
ference of  temperature  becomes  imperceptible. 

Now,  all  this  helps  us  to  understand  what  happens 
at  the  time  of  the  "  Rust  Moon."  In  the  nights 
of  April  and  May  the  temperature  of  the  air  is 
often  not  more  than  8°  to  9°  above  freezing-point. 


134  A   DAY   IN   THE   MOON 

Then,  as  the  result  of  nocturnal  radiation,  the 
ground  may  cool  down  to  one  or  more  degrees 
below  freezing-point.  The  plants  are  subjected  to 
the  same  cooling  process,  and  are  frost-bitten.  Now 
when  this  takes  place,  it  is  under  a  clear  sky,  and 
if  the  Moon  is  above  the  horizon  it  shines  in  all 
its  splendour.  If,  on  the  contrary,  the  weather  is 
cloudy,  the  Moon  will  not  be  visible,  and  there 
will  be  no  frost  on  the  ground — unless,  of  course, 
the  general  temperature  of  the  air  falls  below 
freezing-point. 

It  is  therefore  true,  as  the  gardeners  assert,  that 
with  the  same  general  conditions  of  temperature,  a 
plant  may  be  frozen  or  not  frozen  according  as 
the  Moon  is  visible  or  hidden  behind  the  clouds. 
But  once  more,  the  moonlight  is  here  only  an 
indication  of  the  fact  that  the  sky  is  clear,  and  it 
is  on  account  of  this  clear  sky  that  the  night  cools 
down  ;  but  this  freezing  takes  place  just  the  same 
when  the  Moon  is  not  above  the  horizon.  We 
may  say,  then,  with  Arago  :  "  The  observation  of 
the  gardeners  was  therefore  incomplete,  but  it  would 
be  wrong  to  make  out  that  it  was  false." 

And  now  may  we  ask  why  these  nightly  frosts 
take  place  in  spring,  at  the  end  of  April  and  the 


MOON,   TIDES,   AND   WEATHER     135 

beginning  of  May,  and  not  in  summer  or  autumn  ? 

The  first  reason  is,  that  at  that  time  of  the  year 
winter  is  hardly  ended,  and  the  Sun  has  not  had 
the  time  to  warm  the  Earth,  whilst  later  on,  the 
loss  of  heat  by  cooling  down  in  the  night  does  not 
equal  the  excess  of  heat  stored  up  during  the  day. 

To  this  chief  reason  another  must  be  added. 
We  know  what  an  important  part  water,  in  a 
vaporised  state,  plays  in  maintaining  and  equalising 
the  temperature  of  our  atmosphere.  Well,  the 
quantity  of  this  vapour  is  always  varying,  and  we 
have  proof  of  this  every  day  in  the  changing  indica- 
tions of  the  hygrometer. 

Since  the  invention  of  that  instrument  physicists 
and  meteorologists  have  studied  its  tabulated  results, 
and  this  is  what  they  find. 

The  total  amount  of  vapour  in  the  air  increases 
constantly  from  spring  till  the  month  of  August, 
usually  the  hottest  time  of  the  year.  But  from 
September  it  decreases,  and  reaches  its  minimum 
precisely  in  the  month  of  April,  the  very  time  when 
it  is  most  necessary  for  counterbalancing  nocturnal 
radiation. 

So  in  spring  everything  combines  to  give  us 
chilly  nights  and  to  make  the  Moon  fall  under 


136  A   DAY   IN   THE   MOON 

the  suspicion  of  having  a  cooling  effect,  of  which 
it  is  quite  innocent. 

But  does  this  mean  that  the  Moon  has  no  effect 
on  plants  ? 

It  would  be  very  rash  to  make  such  a  statement 
after  merely  examining  the  theory  of  the  "  Rust 
Moon." 

We  must  look  at  the  problem  from  another  point 
of  view,  and  this  is  what  we  are  going  to  do. 


3     H 


IX 


THE   MOON,   VEGETATION,   AND 
ORGANIC   LIFE 

THE  question  of  the  influence  of  the  Moon  on 
plants  is  as  old  as  the  world,  and  about  every 
twenty-five  years  we  find  some  bold  spirit  who 
does  not  disdain  to  break  a  lance  in  its  defence. 

In  a  little  book  on  Meteorology  that  is  very 
popular  in  the  province  of  Berry,  M.  Larcheveque 
writes  that,  according  to  his  investigations,  there  is 
among  the  people  of  central  France  a  very  strong 
belief  in  the  influence  of  the  Moon  on  planting, 
sowing,  etc.  For  instance,  it  is  held  that  one 
should  plant  and  sow  and  prune  trees  at  the  New 
Moon.  The  first  growth  from  the  seed  and  the 
subsequent  progress  of  the  plant  will  be  more 
rapid  and  vigorous  if  these  operations  are  carried 
out  at  the  New  Moon. 

This  is  the  theory.  From  inquiries  I  have  made 
in  a  good  many  places  I  find  that  it  may  be  taken 


138  A   DAY   IN   THE   MOON 

to  be  a  very  widespread  opinion.  One  comes  across 
it  in  much  the  same  form  in  all  the  countries  of  the 
world. 

But — and  this  is  the  main  point  of  the  matter — 
this  same  theory  has  been  knocked  to  pieces  by 
a  fair  number  of  men  of  science,  and  the  popular 
exponents  of  learning  have  boldly  taken  up  the 
cry. 

"  These  are,"  they  say,  "  nothing  but  old  women's 
stories,  to  which  we  need  pay  no  attention." 

Have  you  remarked  that  often  the  savants  are 
just  those  who  know  Nature  the  least  ? 

I  have  met  with  mathematicians  who  could  hardly 
distinguish  a  maize  plant  from  a  leek  ;  physicists 
ignorant  of  the  most  elementary  principles  of 
physiology  ;  and  geologists  who,  on  the  other 
hand,  had  not  opened  a  book  on  physics  for  twenty 
years. 

This  exaggerated  specialism,  with  its  disregard 
for  all  that  is  outside  its  scope,  produces  the  most 
deplorable  results. 

Men  of  science  who  boast,  as  they  have  a  right 
to  do,  of  the  experimental  method,  and  sometimes 
practise  it,  are  too  often  mere  "  men  of  the  labora- 
tory," and  lose  sight  of  Nature. 


From  the  Lunar  Atlas  of  Lavy  and  Puiseux. 

NORTHERN  HORN  OF  THE  MOON. 

(Reversed  image.) 


138! 


MOON,  VEGETATION,  ORGANIC  LIFE  139 

Astronomers  in  general  treat  with  contempt  any 
possible  influence  of  the  Moon  on  vegetation,  and 
the  meteorologists  do  much  the  same. 

If  the  explanation  of  a  fact  is  not  available,  men 
refuse  to  accept  it  as  authentic.  The  whole  history 
of  science  supplies  us  with  many  instances  of  this. 

Remember  how  the  Academicians  of  a  former 
day  denied  that  stones  could  fall  from  the  sky  ; 
denied  the  facts  of  somnambulism  and  hypnosis  at  a 
time  when  these  phenomena  were  not  accurately 
studied  ;  denied  the  very  real  fact  of  lightning 
coming  down  in  the  form  of  a  ball  of  fire,  etc. 

It  seems  to  me  that  there  is  something  of  the 
same  kind  going  on  with  regard  to  the  Moon  ; 
instead  of  having  recourse  to  the  experimental 
method,  people  are  content  to  deliver  dissertations, 
and  imitate  the  very  methods  of  the  Aristotelians 
and  Scholastics  that  they  rail  at ! 

A  series  of  scientific  experiments  might  be  carried 
out  under  due  supervision,  but  I  know  of  no 
astronomers  or  meteorologists  who  have  "  resigned 
themselves  "  to  such  labours  in  order  to  study  the 
subject  with  which  we  are  occupied. 

Without  taking  one  side  or  the  other  as  to  this 
alleged  influence  of  the  Moon,  I  thought  the  best 


1 40  A   DAY   IN   THE   MOON 

plan  would  be  to  hear  the  evidence  of  the  rival 
camps. 

Let  us  listen  first  to  M.  Henri  Ayme,  the 
Secretary  of  the  Agricultural  Syndicate  of  Lagnes 
in  the  department  of  Vaucluse : 

"  I  am  not  one  of  those  who  think  that  science 
has  discovered  everything,  and  that  one  should 
reject  without  examination  whatever  it  cannot  ex- 
plain. But  if  something  that  cannot  be  explained 
is  to  be  taken  as  certain,  I  consider  that  it  ought 
to  be  supported  by  serious  proofs  from  experience. 
So  if  I  am  convinced  of  the  absence  of  any  influence 
from  the  Moon  in  the  region  of  vegetable  physiology, 
this  is  not  because  such  an  influence  would  be 
inexplicable,  but  it  is  above  all  because  during 
twenty-five  years  of  agricultural  practice  I  have 
never  found  any  seriously  established  fact  to  support 
this  belief,  and  because  I  can  bring  very  precise 
facts  against  it. 

"  In  our  country  the  belief  in  the  influence  of 
the  Moon  is  far  from  having  the  force  of  an  axiom, 
witness  the  farmer  who  said  to  me  : 

" '  We  know  the  Moon  can  do  nothing  to  our 
crops,  but  one  hears  it  so  much  talked  about  that 
it  always  has  some  effect  on  the  imagination.' 


MOON,  VEGETATION,  ORGANIC  LIFE  141 

"  The  facts  cited  in  support  of  it  cannot  be  taken 
as  indisputable.  Let  us  see  how  this  is. 

"There  is  a  widespread  belief  that  trees  pruned 
at  the  Old  Moon  grow  less  strongly  than  if  the 
pruning  is  done  during  the  New  Moon  ;  but  at 
the  same  time,  according  to  the  popular  belief, 
there  is  a  day  that  is  specially  unlucky  for  such 
work.  It  is  the  last  Wednesday  of  the  lunar 
month  ;  so  it  is  an  accepted  idea  that  a  tree  cut 
on  that  day  will  not  send  out  a  new  shoot,  and 
this  to  such  a  point  that  one  is  recommended  to 
choose  the  day  for  cutting  away  brambles  and 
noxious  plants.  Here  is  what  a  farmer  told  me  : 

" ( One  year,  being  very  pressed  with  work,  I 
began  to  prune  six  young  mulberry  trees,  without 
taking  much  thought  about  the  day  or  the  Moon. 
When  I  had  pruned  three  of  them  it  occurred  to 
me  that  it  was  the  last  Wednesday  of  the  Moon. 
I  left  my  work  unfinished,  feeling  quite  sure  that 
I  had  killed  my  three  trees,  and  at  the  New  Moon 
I  came  back  to  them  and  pruned  the  three  remaining 
ones.  But  afterwards  I  could  not  see  the  least 
difference  between  those  that  ought  to  die,  and 
those  that,  according  to  the  popular  belief,  ought 
to  grow  vigorously.' 


142  A   DAY   IN   THE   MOON 

" '  That,'  I  replied,  '  is  an  experience  that  ought 
really  to  make  you  lose  all  your  wonderful  con- 
fidence in  the  Moon.' 

"  And  here  are  several  other  instances  of  which 
I  have  been  a  witness  : 

"  One  day  we  were  busy  planting  potatoes.     A 
neighbour  passed  by  and  addressed  us  thus  : 
"  '  So  you  want  to  have  a  crop  of  little  beads  ? ' 
"  '  How  is  that  ?  ' 

" '  The  Moon  is  no  good  to-day  for  the  work 
you  are  doing.  You  will  have  for  your  crop  a 
lot  of  potatoes,  but  they  will  be  very  small ;  the 
Moon  has  no  force.' 

"  You  see,  he  spoke  very  confidently.  When 
we  dug  the  potatoes  there  was  nothing  out  of 
the  way  in  their  number,  but  they  were  of  splendid 
size  ;  and  this  made  us  say  that  if  the  Moon  had 
had  all  its  force  on  the  day  we  planted  them,  they 
would  have  been  as  big  as  pumpkins. 

"  One  day  I  was  engaged  in  grafting  an  apricot  tree, 
when  a  professional  grafter  noticed  what  I  was  doing. 
"  '  What  !  grafting  to-day  !     But  the  Moon  ?  ' 
" 1 1  must  tell  you  I  have  not  consulted  her.' 
"  The  professional,  with  a  smile  of  pity  for  my 
ignorance,  was  so  good  as  to  say  to  me  : 


H    IS 
H     > 


R  S 

w  J« 

H  0 

a  *• 

o  « 


o    a 
o    - 


- 

I 

Q    W 
W  S 

w 

w 

H 


" '  The  graft  will  take,  but  the  tree  will  not 
bear  fruit — the  Moon  is  New,  but  that  is  no  good 
for  grafting  ! ' 

"  My  graft  was  a  success,  and  still  better,  the 
following  year  it  gave  me  six  fruits.  Twenty  years 
have  gone  by.  In  that  time  my  apricot  has  become 
a  fine  tree,  which  has  always  been  very  fruitful, 
despite  the  prophecy  that  condemned  it  to  sterility. 

"  As  to  wood  being  liable  to  be  worm-eaten 
according  to  the  state  of  the  Moon  when  it  is 
cut,  I  have  no  belief  in  it,  for  I  have  always  had 
my  woodcutting  done  during  the  wane  of  the 
Moon,  and  this  has  been  no  obstacle  to  the 
worms  attacking  it. 

"  As  for  the  story  of  wood  floating  or  going 
to  the  bottom  of  the  water  according  as  the  Moon 
was  Old  or  New  when  it  was  cut,  this  is  the  first 
time  I  have  heard  of  it.  I  should  like  to  witness 
the  experiment,  as  to  the  success  of  which  I  have 
plenty  of  reasons  for  doubt. 

"  Many  gardeners  take  no  notice  of  the  phases 
of  the  Moon.  They  are  content  to  do  their 
sowing  at  the  most  convenient  times,  and  succeed 
just  as  well  as  those  who  consult  the  Moon  on 
every  occasion. 


144  A   DAY   IN   THE    MOON 

"  I  might  quote  many  more  examples  to  show 
that  this  belief  in  the  influence  of  the  Moon 
rests  on  no  serious  facts,  that  it  is  only  a  popular 
prejudice  very  difficult  to  uproot,  and  based  on 
the  agricultural  knowledge,  or  rather  ignorance, 
of  two  hundred  years  ago. 

"  I  remember  having  read  La  Maison  rustique 
du  XVIIe  Siecle,  a  big  folio  of  1,200  pages,  in  which 
this  belief  in  the  Moon  has  the  place  of  honour, 
and  is  made  to  explain  how  to  be  successful,  just 
as  one  explains  a  chess  opening. 

"At  that  time  it  was  not  only  agriculture  that 
was  subject  to  the  Moon,  all  knowledge  was  derived 
from  the  science  of  the  stars.  To  give  only  one 
instance,  doctors  had  a  day  of  the  Moon  for 
giving  medicine  to,  or  bleeding,  those  of  phlegmatic, 
sanguine,  or  hypochondriac  temperaments. 

"  To-day  medical  science  has  got  rid  of  these 
prejudices. 

"  Let  us  hope  that,  to  its  great  advantage,  agricul- 
ture will  do  the  same." 

So  speaks  M.  Ay  me. 

Is  it  exactly  "  to  the  great  advantage "  of 
agriculture  that  it  should  deny  the  existence  of  any 
lunar  influence  on  vegetation  ? 


MOON,  VEGETATION,  ORGANIC  LIFE  145 

That  is  precisely  the  point  of  the  difficulty, 
and  we  shall  see  other  and  as  serious  combatants 
entering  into  the  debate  on  the  opposite  side. 

In  an  extremely  interesting  paper  written  by  a 
horticulturist,  under  the  title  of  Action  mtale  de  la 
Lune,  M.  Galle-Defond  (of  Port-de-Piles,  Vienne) 
has  put  together  some  notes  that,  to  my  mind, 
meet  in  very  clear  and  precise  language  the 
objections  above  stated. 

Here  are  the  rules  which  he  deduces  from 
numerous  experiments. 

He  first  of  all  remarks  that  the  New  Moon 
appears  to  be  favourable  to  the  ascent  of  the  sap 
in  plants,  which  therefore  grow  more  vigorously 
at  this  period  of  the  lunar  month. 

From  this  he  believes  he  can  deduce  different 
methods  of  treatment  for  various  kinds  of  plants, 
according  to  the  results  he  wishes  to  obtain. 

In  the  case  of  carrots,  radishes,  salsifies,  turnips, 
leeks,  and  beet,  all  belonging  to  the  class  of  plants 
cultivated  for  their  roots,  the  sowing  should  be 
done  from  the  5th  to  the  I5th  day  of  the  lunation. 

But  aubergines,  chervil,  chicory,  cabbages,  lettuces, 
onions,    parsley,    tomatoes,    haricots,    green     peas, 
etc.,  and   finally  cucurbitaceous  plants,  melons  and 
10 


146  A  DAY   IN   THE   MOON 

cucumbers,  should  be  sown  and  planted  during 
the  period  of  the  waning  Moon. 

According  to  this  observer,  the  cucurbitaceous 
plants  in  particular  have  been  the  subject  of  con- 
clusive experiments. 

All  this  goes  to  confirm  the  old  saying  :  "  If 
the  Moon  is  lost  the  beans  are  spoilt." 

Popular  wisdom  would  thus  have  some  good 
in  it. 

It  will  be  seen  that  here  there  is  no  question  of 
sowing  on  a  Wednesday  rather  than  any  other 
day  ;  one  must  not  exaggerate  anything. 

If  the  Moon  exerts  any  influence  on  vegetation 
it  would  therefore  be  by  being  favourable  to  the 
rise  of  the  sap  during  the  first  part  of  the 
lunation. 

This  principle  once  admitted,  it  is  easy  to  under- 
stand the  method  used  by  M.  Galle-Defond,  who 
varies  the  times  of  sowing  according  to  the  results 
to  be  obtained. 

But  does  the  sap  between  the  time  of  New  Moon 
and  Full  Moon  rise  more  abundantly  than  during 
the  following  days  ?  This  is  the  whole  problem. 

There  seems  no  doubt  that  the  question  can  be 
solved  when  reduced  to  this  form,  but  the  experi- 


MOON,  VEGETATION,  ORGANIC  LIFE  147 

ments  must  be  carried  out  with  method  and 
precision.  Certain  plants  seem  to  be  specially 
adapted  for  the  test. 

"  In  the  cultivation  of  mushroom  beds,"  says 
M.  Cordier,  a  gardener  of  Luneville,  "  I  have 
always  remarked  that  there  was  as  abundant  a  crop 
between  the  8th  and  the  I5th  day  of  the  lunation 
as  during  all  the  rest  of  the  month  put  together, 
and  as  the  development  of  the  mushroom  takes 
4  to  6  days,  the  rise  of  the  sap  would  thus 
correspond  to  the  first  days  of  the  Moon. 

"  A  second  observation  refers  to  the  cultivation 
of  the  melon.  I  believe  I  have  very  often  re- 
marked that  the  fruit  formed  much  better  during 
the  Old  Moon  than  during  the  New  ;  and  as  to 
obtain  well-formed  fruit,  one  must  avoid  producing 
an  excessive  supply  of  sap,  whether  by  watering 
or  by  heat — it  would  seem  that  the  New  Moon 
produces  this  excess  of  sap,  which  in  normal  times 
one  can  avoid." 

With  regard  to  the  cultivation  of  the  beetroot, 
M.  Compiegne  and  his  sons,  at  Cremarest  (Pas-de- 
Calais),  have  remarked  a  point  that  confirms  the 
preceding  observations.  If  one  cuts  a  beet  across, 
one  can  count  concentric  circular  rings  around  its 


148  A   DAY   IN   THE   MOON 

core  ;  now  the  number  of  these  rings  is  equal  to 
that  of  the  revolutions  of  the  Moon  since  the 
springing  up  of  the  plant. 

These  extremely  interesting  points  may  be  com- 
pared with  others  that  are  less  known. 

M.  Galle-Defond  tells  us  that  one  of  his  friends, 
a  planter  in  America,  has  declared  to  him  that 
some  kinds  of  trees  have  marked  on  their  cross 
sections  not  only  the  rings  indicating  the  years 
of  growth,  but  also  what  really  are  concentric  lunar 
circles. 

The  same  remark  is  made  by  M.  Jacques,  a 
landed  proprietor  in  New  Caledonia,  where  for 
several  years  he  has  been  exploiting  great  tracts  of 
forest. 

"  In  France,"  he  tells  us,  "  trees  are  only  cut 
in  winter,  for  the  excellent  reason  that  if  the  thinning 
is  done  in  the  winter,  when  the  circulation  of  the 
sap  is  least  active,  the  trees  continue  to  grow  better, 
while  those  that  are  thinned  out  in  summer,  in 
June  or  July,  for  instance,  either  grow  badly  or 
not  at  all.  Further,  it  has  undoubtedly  been  shown 
that  wood  cut  in  summer  does  not  keep  well, 
and  soon  after  it  is  felled  is  attacked  by  mushroom 
growths  and  insects,  which  cause  it  to  rot  quickly 


Photograph  by  G.  E.  Hale. 


THE  MOON'S  SURFACE. 


148] 


MOON,  VEGETATION,  ORGANIC  LIFE  149 

and  make  it  useless  for  any  purpose.  This  can 
be  very  well  explained  by  a  kind  of  fermentation 
taking  place  in  the  tree  if  it  is  cut  down  at  the 

D      i 

moment  when  it  contains  an  abundance  of  sap. 

"Here  the  Moon  is  not  to  blame,  for  it  is  the 
Sun  that  favours  this  great  production  of  sap,  that 
afterwards  leads  to  decay. 

"  But  in  New  Caledonia,  where  the  temperature 
is  from  73°  to  77°  in  winter  and  from  77°  to  86° 
in  summer,  the  rapid  decomposition  of  wood  cut 
during  the  New  Moon  cannot  be  attributed  to 
the  same  causes,  unless  it  is  admitted  that  in  tropical 
countries  the  sap  circulates  in  greater  abundance 
during  the  New  than  during  the  Old  Moon. 

"  I  must  tell  you  that  at  the  outset  I  had  no 
belief  whatever  in  any  influence  of  the  Moon  on 
the  preservation  of  wood.  It  was  all  very  well 
for  the  natives  to  say  to  me,  *  Him  not  good  to 
cut  at  present,  him  wait  to  cut  till  good.'  I  paid 
no  attention,  and  I  had  a  costly  experience  of  it. 

"  For  all  the  woods,  even  those  of  the  hardest 
structure,  that  were  cut  during  the  New  Moon, 
were  very  soon  worm-eaten,  while  those  felled 
during  the  Old  Moon  remained,  even  after  the 
lapse  of  many  years,  in  an  excellent  state  of 


1 50  A   DAY   IN   THE   MOON 

preservation.  And  this  was  not  in  any  one  month 
rather  than  another,  for  I  had  the  curiosity  to 
repeat  the  experiment  during  every  lunar  month  of 
the  year,  and  the  result  was  always  the  same. 

"  The  Bancoulier  tree,  for  instance,  which  is  very 
soft  wooded,  if  felled  and  cut  up  in  the  New  Moon 
literally  went  to  dust  in  six  months  ;  the  same 
wood  felled  and  cut  up  during  the  Old  Moon  kept 
without  change  for  years. 

"It  does  not  follow  from  this  that  the  Moon 
exerts  a  direct  action  on  timber  cut  during  this  or 
that  phase,  but  I  simply  note  the  fact  that  wood 
cut  during  a  certain  period  of  the  lunar  month 
rapidly  deteriorates,  while  that  cut  in  another  period 
of  the  Moon  keeps  in  the  normal  way." 

We  might  quote  here  M.  Galle-Defond's  experi- 
ments on  the  cultivation  of  fruit  trees.  We  shall 
content  ourselves  merely  with  noting  that,  according 
to  him,  it  is  most  important  not  to  plant  any  fruit 
tree  or  shrub  during  the  first  fortnight  of  the 
Moon  if  one  wants  to  have  a  good  supply  of  fruit 
from  it. 

To  sum  up,  it  would  seem  that  the  Moon  exerts 
some  influence  upon  vegetable  life,  and  if  in  our  lands 
the  experiments  are  not  all  conclusive,  it  is  because 


MOON,  VEGETATION,  ORGANIC  LIFE  151 

frequently  the  lunar  action,  perhaps  a  very  slight 
one,  is  counteracted  by  changes  of  the  weather  which 
diminish  its  effect  or  neutralise  it  altogether. 

And  the  best  proof  of  it  is  afforded  us  by  facts 
observed  in  tropical  countries,  where  there  is  nothing 
to  disturb  the  action  of  our  satellite. 

If  these  conclusions  are  justified,  we  ought  to  be 
able  to  note  this  lunar  influence  all  the  more  clearly 
as  we  turn  our  attention  to  vegetable  phenomena 
of  a  more  rudimentary  class. 

And  this  is  precisely  what  is  shown  by  the 
experiments  of  M.  Carbonnier  on  cryptogamic 
vegetation,  principally  that  which  grows  in  stagnant 
waters. 

The  maximum  intensity  of  growth  of  this  kind 
always  corresponds  to  the  time  of  the  Full  Moon. 

These  are  undoubted  facts  ;  whatever  be  the 
explanation,  they  will  remain  none  the  less  certain. 

To  whatever  theory  we  may  appeal,  it  is  a  fact 
known  to  all  botanists  that  the  growth  of  plants 
depends  on  the  carbonic  acid  diffused  in  the  atmo- 
sphere ;  now  this  phenomenon  takes  place  above 
all  under  the  action  of  light.  No  light,  no  pro- 
duction of  chlorophyll,  and  therefore  no  vegetable 
growth. 


152  A  DAY   IN   THE   MOON 

One  might  thus  explain  why  seeds  sown  at  the 
New  Moon  develop  more  rapidly  than  if  they 
had  been  placed  in  the  ground  at  the  Full 
Moon. 

In  the  former  case,  when  the  seedlings  push 
through  the  surface  of  the  ground  the  Moon  gives 
them  some  of  the  light  they  need  to  absorb  carbon 
and  grow  ;  in  the  second  case  they  come  out  of 
the  ground  when  the  Moon  is  below  the  horizon, 
and  are  thus  deprived  of  its  luminous  rays  during 
the  nights. 

And  then,  who  can  tell  us  what  is  the  inner 
mechanism  of  vegetable  growth,  presiding  over  the 
life  of  the  microbe  as  well  as  that  of  more  highly 
organised  structures  ?  What  is  the  action  of  the 
rays  of  the  spectrum,  of  chemical  radiations,  and  of 
unknown  vibrations  ? 

Truly,  instead  of  denying  facts,  we  would  do 
better  to  study  them  more  closely.  The  explanation 
will  come  after  that. 


ASTRAL   INFLUENCES  AND 
ASTROLOGERS 

THE  search  for  the  causes  of  things  is  most  cer- 
tainly a  deep-seated  tendency,  a  law  of  the  mind — 
a  law  that  dominates  it  forcibly  and  inevitably — for 
through  all  time  we  see  humanity  seeking  to  find 
behind  the  effects  it  has  observed  a  reason  capable 
of  giving  a  logical  explanation  of  them. 

If  those  causes  eluded  his  search  through  his 
invincible  ignorance,  man  very  often  sought  for  an 
explanation  of  the  phenomena  around  him  in  the 
forces  of  Nature  personified  for  the  purpose,  and 
endowed  by  his  imagination  with  the  most  ex- 
travagant powers. 

Thus,  as  the  vault  of  the  skies  attracted  the 
attention  of  primitive  peoples,  the  constellations 
were  soon  supposed  to  play  a  preponderating  part 
in  human  destinies  and  in  all  the  actions  of  life. 

Virgil   tells    us    how  Orion   was    associated  with 


i54  A   DAY   IN   THE    MOON 

the  coming  of  rain,  and  the  Pleiades  forecasted 
stormy  weather. 

But  the  presence  of  the  Sun  and  Moon  or  the 
planets  above  the  horizon,  and  later  on  the  calcu- 
lated positions  of  the  heavenly  bodies,  became,  in 
the  hands  of  the  astrologers,  the  basis  of  a  complete 
science  for  the  prediction  of  the  future. 

The  Sun,  as  we  know,  in  the  course  of  the  year 
pays  a  visit  to  each  of  the  twelve  constellations  of 
the  zodiac.  An  individual  born  in  such  or  such  a 
month  was  therefore  supposed  to  be  under  the 
influence  of  this  or  that  constellation.  Thus 
fatalism  had  a  fine  field. 

Don't  smile  at  all  this.  Why,  even  to-day  there 
are  plenty  of  almanac-makers  that  would  think  they 
were  not  living  up  to  their  reputation  if  they  did 
not  give  horoscopes  taken  from  the  position  of  the 
Sun  in  each  sign  of  the  zodiac. 

Were  you  born  under  the  sign  of  the  Bull  or 
the  Ram  ?  You  are  assured  of  material  prosperity. 
The  Scorpion  predicts  a  contrary  destiny  for  you  ; 
the  Lion  presages  heroes  ;  the  Virgin  forecasts  a 
pure-minded  disposition  ;  Capricorn  brings  riches — 
and  so  forth. 

Unfortunately  the  diversity  of    the  life -destinies 


From  the  Photographic  Atlas  of  the  Paris  Observatory. 

REGION  BETWEEN  THE  "MARE  IMBRIUM  "  AND  THE  NORTH  POLB 
OF  THE  MOON. 

At  the  top  are  the  Mare  Imbrium  (Sea  of  Rains),  I,aplace~  Promontory  and 
the    Sinus  Iridum   (Gulf   of    Rainbows).     I^wer   down,    the   large   mountain   ring 
with  a  dark  interior  is  Plato.     Below  this  is  the  Mare  Frigoris  (Sea  of  Cold)  and 
then  the  North  Pole  of  the  Moon  with  the  mountainous  region  around  it. 
.  (Reversed  image.) 


154] 


ASTRAL  INFLUENCES,  ASTROLOGERS    155 

of  men  born  under  this  or  that  sign  has  always 
been  so  great  that  the  astrologers  soon  found  the 
need  of  additional  explanations. 

It  was  then  that  they  brought  in  the  action  of 
the  Moon  and  the  planets. 

Mercury  was  the  patron  of  the  arts  ;  Mars 
inspired  to  war  ;  Venus  could  only  keep  to  her 
mythological  character  ;  Jupiter  indicated  to  mortals 
born  under  its  influence  that  they  were  destined  to 
the  greatest  triumphs  ;  witness  this  passage  from  a 
book  on  Astrology  of  the  days  of  Louis  XIII  : 
<c  Jupiter  in  the  first  sign  of  the  zodiac  makes 
nobles,  men  of  power,  bishops,  rulers,  sages, 
philosophers,  merchants,  bankers." 

Saturn  was  associated  with  the  greatest  sorrows ; 
it  was  considered  an  unlucky  star.  What  would 
they  have  said  of  Uranus  and  Neptune  ?  But 
they  were  unknown  at  that  time. 

All  this  seemed  quite  natural,  and  no  one  was 
tempted  to  laugh  at  it  ;  nevertheless,  one  thinks 
one  must  be  dreaming  as  one  reads  some  of  the 
manuscripts  of  the  Middle  Ages  and  the  extra- 
ordinary horoscopes  they  contain. 

The  doctrines  of  the  astrologers  were  held  in 
high  honour  among  the  Arabs,  and  from  them 


156  A   DAY   IN   THE   MOON 

passed  into  Spain  ;  but  it  was  especially  on  the 
return  of  the  Crusaders  from  the  East  that  they 
spread  over  Western  Europe. 

Then  kings  and  princes  had  their  official  astro- 
logers, and  these  poor  people  had  too  often  reason 
to  repeat  the  words  of  Scripture — "  No  lite  confidere 
in  prindpibus  "  ("  Put  not  your  trust  in  princes  "). 

Flattery,  generally  so  successful  with  the  great, 
was  often  no  help  to  the  astrologers,  and  they  had 
to  rack  their  brains  to  find  something  better. 

Thus  one  day,  when  he  was  in  a  bad  humour, 
Louis  XI  sent  for  his  astrologer  Galeotti,  and  put 
a  very  embarrassing  question  to  him. 

"  As  by  your  own  claim  you  know  everything," 
said  the  king  to  him,  "  tell  me  when  you  will 
die." 

Alas  for  Galeotti  !  He  knew  the  king  had  told 
his  people  that  as  soon  as  they  had  a  sign  from 
him  they  were  to  put  the  astrologer  into  a  sack  and 
throw  him  into  the  river. 

But  his  ready  wit  saved  him  from  this  awkward 
situation. 

"  Sire,"  he  replied  at  once,  "  I  have  carefully 
consulted  the  stars  on  this  subject,  and  they  tell 
me  I  shall  die  just  three  days  before  your  Majesty." 


ASTRAL  INFLUENCES,  ASTROLOGERS    157 

The  king  was  very  superstitious,  but  perhaps  he 
did  not  believe  this  ;  nevertheless,  he  took  care  not 
to  carry  out  his  plan.  "  After  all,"  he  thought, 
"  one  can  never  be  certain." 

Strange  to  say,  and  to  a  certain  point  this  is  an 
excuse  for  the  almost  universal  belief  in  Astrology 
at  a  time  when  modern  Astronomy  had  not  yet 
revealed  the  mechanism  of  the  heavens,  the 
astronomers  themselves  gave  the  example,  and  most 
of  them  united  the  professions  of  astrologer  and 
astronomer. 

It  is  true  that  many  of  them  regarded  Astrology 
as  only  a  necessary  expedient  for  earning  their  daily 
bread  and  an  indirect  means  of  enabling  them  to 
devote  themselves  to  more  serious  work. 

In  his  Ephemerides  for  1469  Johann  Miiller, 
who  is  better  known  under  the  name  of 
"  Regiomontanus,"  investigates  the  question  of  the 
aspects  of  the  Moon  under  which  it  is  best  to 
perform  the  operation  of  blood-letting,  and  on 
what  parts  of  the  human  body  the  various  signs  of 
the  zodiac  have  a  special  influence. 

We  find,  indeed,  such  indications  in  an  old 
drawing  in  a  manuscript  in  the  library  of  Bourges. 

Taurus  the  Bull  influences  the  neck  and  the  upper 


158  A   DAY   IN   THE    MOON 

part  of  the  throat  ;  Cancer,  the  chest,  lungs, 
stomach,  etc. 

Stoefler,  an  able  mathematician,  who  was  a  pro- 
fessor at  Tubingen,  believed  in  the  influence  of  the 
heavenly  bodies  on  events  here  on  Earth. 

Having  calculated  that  there  would  be  a  con- 
junction of  the  planets  Mars,  Jupiter,  and  Saturn  in 
the  month  of  February  1 524,  he  predicted  a  universal 
deluge  at  that  date. 

Could  it  be  otherwise,  seeing  that  this  heavenly 
phenomenon  would  take  place  in  the  sign  of  the 
Fishes  ? 

The  prophecy  made  a  great  stir,  and  a  doctor  of 
Toulouse,  named  Auriol,  took  it  so  seriously  that 
he  immediately  had  a  great  vessel  constructed  on 
the  plan  of  Noah's  ark. 

February  came — and  it  was  the  driest  month  of 
the  year. 

It  is  said  that  Jerome  Cardan  drew  a  horoscope 
for  Edward  VI. 

But  he  piled  up  such  a  series  of  unsuccessful 
prophecies  that  at  last,  disgusted  with  his  failures, 
he  ended  by  predicting  his  own  death  for  the 
year  1570. 

As    if  he   meant   to   show   that,   once   in   a   way, 


ASTRAL  INFLUENCES,  ASTROLOGERS    159 

his  prophecies  could  be  correct,  he  starved  himself 
to  death. 

Tycho  Brahe  (1546—1601)  did  not,  as  a  rule, 
make  any  distinction  between  Astrology  and  As- 
tronomy ;  these  two  sciences  were  only  one  at 
that  time,  or  rather  the  true  Astronomy  had  not 
yet  come  into  existence. 

Though  he  had  something  like  a  real  vocation 
for  the  study  of  the  stars,  Tycho  had  all  the  trouble 
in  the  world  to  accomplish  his  plans. 

His  father,  Otho  Brah£,  Lord  of  Knudstrup,  in 
Scania,  had  been  brought  up  in  the  complete 
ignorance  that  then  befitted  a  nobleman.  How- 
ever, he  consented  to  let  his  son  go  first  to 
Copenhagen,  and  then  to  Leipsic,  to  study  law, 
but  Tycho  eluded  his  tutor's  vigilance  and  spent 
all  his  nights  in  the  study  of  the  skies. 

Though  of  a  kindly  and  generous  character,  and 
endowed  with  the  noblest  feelings,  he  had  a  hasty 
and  violent  temper.  This  was  the  source  of  end- 
less trouble  for  him  that  followed  him  through 
all  his  life. 

It  appears  that  while  he  was  a  student  at  Leipsic 
he  drew  his  own  horoscope,  and  was  startled  to 
find  that  the  scheme,  where  the  influence  of  the 


160  A   DAY    IN   THE    MOON 

planet  Mars  came  into  it,  presaged  for  him  a  dis- 
figurement in  the  face. 

There  was  nothing  to  justify  this  indication, 
till  one  fine  day  he  picked  a  quarrel  with  one  of 
his  fellow-students  over  a  theorem  in  geometry. 

A  duel  was  arranged.  On  a  dark  night  by  the 
light  of  a  smoky  torch  the  two  opponents  attacked 
each  other  furiously,  and  after  they  had  crossed 
weapons  several  times,  a  sword-cut  took  offTycho 
Brahe's  nose. 

The  horoscope  was  fulfilled. 

Tycho  was  not  too  downcast  at  his  unfortunate 
adventure  ;  his  wound  healed,  and  he  made  him- 
self an  artificial  nose  of  gold,  silver,  and  wax. 
Contemporaries  tell  us  that  the  imitation  was  so 
perfect  that  no  one  ever  noticed  his  loss. 

Even  Kepler,  who  was  to  make  himself  famous 
by  the  discovery  of  his  immortal  laws,  was  obliged 
to  play  the  astrologer. 

At  every  turn  his  works  refer  to  the  wonderful 
properties  of  numbers,  to  disturbing  influences, 
the  conjunction  of  planets,  etc.,  etc. 

He  was  only  twenty-four  years  old  when,  in 
1594,  he  was  appointed  professor  at  Gratz,  in 
Styria.  Besides  his  work  as  a  teacher  he  was  en- 


THE  THREE  CHIEF  MOUNTAIN  RINGS  ARE  (FROM  TOP  TO 
BOTTOM)  THEOPHILUS,  CYRILLUS,  AND  CATHERINE. 

(Erect  image.) 


ASTRAL  INFLUENCES,  ASTROLOGERS    161 

trusted  with  the  making  of  almanacs — predictions 
as  to  the  weather,  horoscopes,  all  that  kind  of 
thing  was  then  very  closely  connected  with  the 
astronomical  figures  relating  to  the  positions  of  the 
stars. 

Later  on  he  had  to  continue  the  practice  of  this 
wretched  profession  in  order  to  support  his  large 
family,  and  he  often  drew  the  horoscopes  of  princes, 
who  summoned  him  to  their  courts  "  to  know 
their  fate  by  the  stars." 

Kepler,  in  reality,  had  no  belief  in  these  practices, 
and  we  have  the  proof  of  this  very  clearly  in  a 
passage  in  his  writings  :  "  What  have  you  to 
complain  of,  you  over-scrupulous  philosophers,  if 
a  daughter  (Astrology),  whom  you  think  foolish, 
supports  a  wise,  though  poor,  mother  (Astronomy)  ; 
if  this  mother  is  tolerated  among  men  more  foolish 
still,  only  for  the  sake  of  these  same  follies  ?  If 
men  had  not  had  the  credulous  hope  of  reading 
the  future  in  the  heavens,  would  you  ever  have 
been  wise  enough  to  study  Astronomy  for  its  own 
sake  ? " 

And  in  fact,  in  Kepler's  days,  alchemists,  astrolo- 
gers, and  magicians  swarmed  to  such  a  degree  that 
L'Estoile  wrote  in  his  Journal  de  Henri  III: 
1 1 


1 62  A   DAY    IN   THE    MOON 

"  In  the  time  of  Charles  IX  these  vermin  had 
secured  such  immunity  in  Paris,  that  there  were 
as  many  as  30,000  of  them,  as  the  chief  of  them 
admitted  in  1572." 

Henri  II  of  France  often  consulted  the  famous 
Nostradamus,  who  wrote  his  Centuries,  a  collection 
of  prophecies  in  which  no  one  ever  understood 
anything — very  likely  not  even  their  author. 

This  work,  of  which  Henri  II  accepted  the 
dedication,  was,  however,  of  this  much  service  to 
Nostradamus,  that  it  led  to  his  being  summoned 
by  the  King,  who  gave  him  100  crowns  in  gold 
and  sent  him  to  Blois  to  draw  the  horoscopes  of 
his  sons,  the  young  princes. 

New  honours  were  lavished  on  Nostradamus  as 
the  result  of  this  mission,  and  later  Charles  IX 
and  Catharine  de*  Medici  attached  him  to  their 
service. 

The  latter  soon  began  to  set  the  very  highest 
value  on  Astrology.  She  spent  absurd  amounts 
of  money  on  building  observatories  merely  for 
the  purpose  of  being  herself  able  to  consult  the 
stars. 

One  of  the  most  famous  of  these  was  that  of 
the  Hotel  de  Soissons.  It  consisted  of  a  column 


ASTRAL  INFLUENCES,  ASTROLOGERS    163 

nearly    100   feet   high,    which    the    pickaxe   of  the 
town  improver  has  spared  to  our  day. 

This  Hotel  de  Soissons  has  a  whole  curious  story 
of  its  own  connected  with  Astrology. 

We  shall  let  Dulaure  himself  tell  it  to  us : 
"  Why  did  this  queen — after  having  built  the 
palace  of  the  Tuileries,  expended  considerable  sums 
upon  it,  and  adorned  it  with  the  work  of  the 
most  famous  artists  and  all  that  luxury  could  desire 
in  the  way  of  comfort  and  elegance — leave  the 
place  for  good  and  all  soon  after  the  building 
was  completed  ?  Why  did  she  take  a  dislike  to 
the  palace,  and,  at  a  time  when  the  finances  were 
exhausted,  buy  the  Abbey  of  Saint-Maur  des  Fosses 
to  erect  a  residence  there  for  herself?  Why  did 
she  then  abandon  this  project,  only  to  take  up 
another,  and  buy  the  convent  of  the  Filles 
Penitentes  ?  Why  did  she  disturb  the  nuns  who 
lived  there  by  transferring  them  to  the  Abbey  of 
Saint-Maur,  and  secularise  the  monks  of  the  latter 
abbey  in  order  to  transfer  them  to  the  Hospital  of 
Saint-Jacques  du  Haut  Pas  ?  Why  was  she  obliged 
to  ask  of  her  son,  the  king,  the  permission  to 
carry  out  these  changes,  and  of  the  Pope  bulls  to 
ratify  these  transfers  and  secularisations,  and  of 


1 64  A   DAY    IN   THE   MOON 

the  Parlement  de  Paris  the  registration  of  all  these 
acts  ?  Why,  finally,  did  she  order  all  these  changes, 
and  especially  give  up  the  Tuileries,  to  build 
and  go  to  live  in  a  new  residence?  Here  is  the 
reason — Catharine  de'  Medici  was  frightened  at 
the  prediction  of  an  astrologer,  who  foretold  that 
she  would  die  in  a  place  called  Saint-Germain.  Now 
the  Tuileries  were  situated  in  the  parish  of  Saint- 
Germain  1'Auxerrois.  '  It  was  at  once  noticed,' 
says  Mezeray,  '  that  she  superstitiously  avoided  all 
the  places  and  churches  that  bore  that  name.  She 
would  not  again  go  to  Saint-Germain-en-Laye,  and 
because  her  palace  of  the  Tuileries  was  in  the 
parish  of  Saint-Germain  in  1'Auxerrois,  she  even  had 
another  built,  namely,  the  H6tel  de  Soissons  near 
Saint-Eustache.' 

"  There  is  something  satisfying  to  self-love 
when  one  sees  ridiculous  actions  on  the  part  of 
powerful  people  who  have  aspired  to  celebrity. 
This  queen,  so  powerful,  so  feared,  so  imperious, 
debased  herself  by  her  stupid  credulity  to  the  level 
of  the  very  lowest  class  of  society.  She  believed  what 
to-day  the  old  women  of  the  most  out-of-the-way 
villages  would  blush  to  believe ;  she  believed 
in  the  predictions  of  magicians,  and  she,  who 


ASTRAL  INFLUENCES,  ASTROLOGERS    165 

struck  terror  into  the  hearts  of  so  many,  was 
herself  terrified  at  the  oracles  of  the  wretched 
astrologer. 

"This  hotel,  which  in  the  fourteenth  century 
had  borne  in  succession  the  names  of  de  Nesle, 
de  Boheme,  and  de  Behaigne,  and  in  the  fifteenth 
that  of  d'Orleans,  then  that  of  the  £  Filles 
Penitentes '  when  the  nuns  of  that  order  occupied 
it,  was  called  the  H6tel  de  la  Reine  in  1571, 
when  it  became  the  property  of  Catharine  de' 
Medici.  After  the  death  of  the  queen  it  was 
called  the  Hotel  des  Princesses,  and  finally  the 
Hotel  de  Soissons  as  at  present. 

"Catharine  de'  Medici  had  had  erected  there, 
after  the  plans  of  Bullant,  and  in  the  angle  of  a 
side  court,  a  fluted  Doric  column  of  great  height, 
to  be  used  by  herself  as  an  observatory.  It  adjoined 
and  was  in  communication  with  the  Hotel  de  la 
Reine.  This  column  is  the  only  structure  belonging 
to  the  Hotel  de  Soissons  that  survives.  It  is  still 
to  be  seen  close  to  the  buildings  of  the  Halles  ; 
it  has  a  winding  stair  in  its  interior.  The  queen 
used  to  ascend  it  to  consult  the  stars,  and  seek  to 
find  in  their  positions  the  promise  of  a  happiness  that 
those  who  reign  amid  crimes  never  find  on  this  earth." 


1 66  A    DAY   IN   THE   MOON 

The  favourite  astrologers  of  Catharine  de'  Medici 
were  R6gnier,  and  a  certain  Cosmo  Ruggieri,  a 
native  of  Florence.  It  was  the  latter  who  made 
the  prediction  as  to  the  place  of  the  princess's  death. 

But  notwithstanding  all  the  precautions  she  took, 
this  is  what  happened.  At  least  it  is  what  certain 
historians  tell  us. 

After  having  fled  from  all  the  Saint-Germains 
in  the  world,  one  day,  when  Catharine  was  at  Blois, 
she  had  a  severe  attack  of  fever  on  hearing  the 
news  of  the  assassination  of  the  Duke  of  Guise. 
At  once  she  sent  in  terror  for  a  priest  and  asked 
his  name. 

"  The  Pere  Saint-Germain,  preacher  to  the  King," 
was  the  reply. 

"  Ah  !  "  exclaimed  Catharine,  "I  am  a  dead 
woman !  " 

And  in  fact  she  died  next  day,  January  5,  1589. 

In  the  following  reigns  there  were  perhaps  fewer 
astrologers,  but  their  influence  did  not  diminish. 

At  the  moment  when  his  son  was  born  Henri  IV 
desired  his  doctor  and  the  astrologer  Lariviere 
to  draw  the  horoscope  of  the  royal  child. 

The  astrologer  got  very  well  out  of  the  business 
by  declaring  that  the  young  prince  was  born  under 


ASTRAL  INFLUENCES,  ASTROLOGERS    167 

the  sign  of  the  Balance,  and  this  was  why 
Louis  XIII,  from  his  very  cradle,  was  surnamed 
"  the  Just." 

So  it  was  a  very  simple  business  ! 

An  astrologer  was  also  on  duty  at  the  birth 
of  Louis  XIV  and  drew  his  horoscope  with  equal 
success. 

How  could  it  have  been  otherwise,  since 
even  the  astronomers  lent  themselves  to  these 
practices  ? 

Many  of  them  even  believed  in  their  forecasts — 
for  instance,  the  famous  Morinus,  who  did  not 
hesitate  to  predict  to  people,  on  all  manner  of 
occasions,  what  would  happen  to  them  at  an  early 
date. 

Thus  it  was  that  he  announced  to  his  colleague 
Gassendi  as  the  time  of  his  death  the  end  of  the 
coming  July  of  1650.  "But,"  the  famous 
Canon  of  Digne  used  to  delight  in  telling  his 
friends,  "  I  was  never  better  than  at  the  fatal 
epoch  marked  out  by  the  prediction  of  Morinus." 

And  a  little  later  have  we  not  the  Comte  de 
Boulainvilliers  in  concert  with  the  Italian  astrologer 
Colonna  predicting  the  death  of  Voltaire  at  the 
age  of  thirty-two.  "  Everyone  knows,"  remarks 


1 68  A   DAY    IN   THE    MOON 

Arago  when  relating  the  fact,  "  how  that  prediction 
was  fulfilled !  " 

Gradually,  however,  the  fashion  seemed  to 
change  and  we  see  the  "  most  excellent  mathema- 
ticians and  extractors  of  quintessences,"  of  whom 
Rabelais  had  made  sport,  turning  their  attention 
to  almanacs  or  "  prognostications." 

Thus  in  this  connection  we  read  in  the  second 
edition  of  the  Astronomic  de  M.  Lalande,  printed 
in  1771,  this  characteristic  passage  : 

"  It  is  not  without  difficulty  that  at  last  the 
philosophic  spirit  has  dissipated  these  errors  ;  at 
the  beginning  of  this  century  people  at  times  came 
to  consult  the  astronomers  of  the  Academic  as  to 
the  future,  and  in  1705  M.  Lieutaud  thought 
it  well  to  print  as  a  preface  to  the  Comaissance 
de  Temps  :  c  No  predictions  will  be  found  here, 
because  the  Academy  has  never  recognised  the 
solidity  of  the  rules  given  by  the  Ancients  for 
predicting  the  future  by  the  relative  positions  of 
the  stars/ 

"  If  one  reads  a  letter  in  the  Mercure  de  France 
of  1763,  in  which  I  told  of  the  anxiety  of  the 
Sultan  of  Turkey  to  obtain  all  the  works  published 
by  the  astronomers  of  the  Academy,  it  will  be 


ASTRAL  INFLUENCES,  ASTROLOGERS    169 

remarked  that  he  asked  especially  for  any 
predictions  made  as  to  the  future  by  the  science 
of  the  stars.  Perhaps  his  Highness  only  wanted 
our  books  of  astronomy  in  the  hope  of  finding 
in  them  the  fate  of  the  Powers,  who  seemed  intent 
on  mutual  destruction." 

Nowadays  no  one  any  longer  ventures  to 
consult  men  of  science  as  to  reading  the  future  in 
the  stars,  but  the  bent  of  the  popular  mind  has  not 
altered. 

Did  not  Napoleon  go  to  have  "  his  good  fortune  " 
told  by  the  celebrated  card-reader  Mademoiselle 
Lenormand  ? 

It  is  not  long  since  I  had  proposals  from  more 
than  one  contemporary  astrologer  to  draw  my 
horoscope. 

The  card-readers  and  the  necromancers  of 
spirit-seances  find  each  year  Paris  newspapers 
ready  to  publish  their  ambiguous  and  grotesque 
predictions. 

The  fortunes  they  make  for  themselves  in  this 
"  noble  profession "  are  one  more  proof  of  the 
ignorance  and  insurmountable  credulity  of  the 
public. 

But  let  us    stop,  for   one    might  write   volumes 


i  yo  A   DAY   IN   THE    MOON 

on  such  a  subject,  and  probably  without  advantage 
to  anyone. 

Let  us  leave  the  astrologers  to  draw  their 
horoscopes.  The  planets  are  too  far  off  to  exert 
an  influence  on  the  life  of  any  one  of  us.  Even 
the  perturbations  they  cause  in  the  earth's  move- 
ments are  infinitesimal. 

But  we  cannot  say  as  much  of  the  Moon,  and 
I  confess  that  here  those  who  take  an  interest  in 
the  influence  of  the  heavenly  bodies  have  a  better 
case. 

What  effect  can  the  Moon  have  on  the  develop- 
ment of  the  animal  organism,  and  what  influences 
come  from  it  ?  This  is  what  it  remains  for  us  to 
examine. 


XI 

THE   ACTION   OF  THE  MOON  ON  MEN 
AND   ANIMALS 

IF  it  may  be  admitted  that  the  Moon  exerts  some 
action  on  the  phenomena  of  vegetation,  one  cannot 
see  a  priori  any  reason  why  animal  growth  should 
not  be,  up  to  a  certain  point,  dependent  on  the 
same  influence. 

Everyone  knows  the  effects  of  spring  on  the 
animal  organism,  and,  as  far  as  I  know,  no  one  has 
found  a  complete  explanation  for  it. 

At  the  moment  when  the  sap  begins  to  rise 
freely  in  the  plants,  it  seems  as  if  at  the  same 
time  a  "  revival  "  comes  over  men  and  animals. 

If,  then,  the  Moon  promotes  by  its  action  the  rise 
of  the  sap,  or  the  chemical  combinations  of  the 
vegetable  cell,  one  can  imagine  the  possibility  of 
a  similar  action  on  the  animal  cell,  which  in  its 
inner  structure  differs  very  little  from  the  former. 

And   in   fact   there    is    no   lack  of  observations 
171 


172  A   DAY   IN   THE    MOON 

bearing  on  this  point.  One  would  want  whole 
volumes  to  classify  them  all. 

M.  Latourte  of  Dieppe  wrote  recently  : 

"  I  keep  some  hens,  and  during  forty  years  I 
have  reared  a  good  number. 

"  Now,  each  time  that  I  put  eggs  to  be  hatched, 
the  chickens  hatched  out  during  the  period  from 
the  First  Quarter  to  the  Full  Moon  break  through 
the  shell  more  easily,  and  are  more  vigorous  than 
their  fellows  who  come  out  in  the  period  from  the 
Last  Quarter  to  the  New  Moon." 

This  confirms  the  observations  of  M.  Galle- 
Defond,  who  is  a  poultry  farmer  as  well  as  a 
horticulturist  : 

"  The  Moon,"  he  writes,  "  is  not  without  some 
influence  on  the  success  or  failure  of  the  hatching 
out  of  chickens  or  goslings." 

The  growth  of  animals  born  at  the  beginning 
of  the  lunation  follows  the  same  rule  as  that  of 
plants.  It  appears  to  be  more  rapid  than  that  of 
animals  born  in  the  waning  of  the  Moon. 

So  perhaps  our  ancestors  were  not  so  foolish 
when  they  preached  their  plan  of  having  their 
hair  cut  and  their  beards  trimmed  at  the  New 
Moon. 


ACTION   ON    MEN   AND   ANIMALS    173 

Even  the  wine  industry  has  the  benefit  of  these 
prescriptions.  So  we  are  told  that  the  racking  of 
the  wine  should  never  be  done  towards  the  end  of 
the  lunar  month. 

It  is  now  known  that  the  fermentation  of  wine 
depends  on  the  development  of  a  micro-organism — 
of  a  cell — and  if  we  admit  the  influence  of  the 
Moon  on  organic  beings,  it  will  be  easily  under- 
stood that  here  too  its  influence  would  come  under 
a  general  law. 

So  we  can  only  repeat  what  we  have  said  in  previous 
chapters  :  Light  is  only  a  form  of  energy,  and  we 
are  very  far  from  having  analysed  all  its  radiations. 

Perhaps  it  is  in  this  mysterious  influence  which 
promotes  the  development  of  the  cell,  and  is 
favourable  to  the  general  activity  of  the  human  body, 
that  we  must  look  for  the  explanation  and  origin 
of  the  word  lunatic \  applied  to  persons  subject  inter- 
mittently to  loss  of  reason  and  attacks  of  madness. 

With  the  ancients  there  was  no  doubt  as  to  the 
action  of  the  Moon  on  the  mental  state  of  certain 
subjects. 

In  a  book  of  1399,  a  learned  history  of  the 
madness  of  Charles  VI  of  France,  we  read  : 

"  The  King,  who  had  recovered  his  health,  kept 


174  A   DAY    IN   THE   MOON 

the  feast  of  Easter  in  his  royal  residence  of  Saint- 
Paul.  .  .  .  Every  one  was  rejoicing  at  his  recovery, 
but  this  happy  state  of  things  did  not  last  long.  That 
same  year  he  relapsed  six  times  into  madness,  either 
at  the  New  or  at  the  Full  Moon." 

If  this  were  an  isolated  fact,  evidently  it  would 
prove  nothing,  but  we  shall  see  that  it  is  corro- 
borated by  other  testimony  of  the  same  kind. 

In  a  work  on  medicine  published  in  1578  by 
Dr.  Joubert  of  Montpellier,  the  falling  sickness, 
or  epilepsy,  as  well  as  melancholy,  are  classed  among 
the  illnesses  that  quite  evidently  depend  upon  the 
course  and  phases  of  the  Moon.  Menuret  con- 
siders skin  diseases  to  be  those  the  recurrences 
of  which  are  most  indisputably  connected  with  the 
lunar  phases.  He  asserts  that  he  himself  had 
observed  in  1760  a  cutaneous  attack  of  a  patient 
increasing  continually  during  the  waning  of  the 
Moon,  and  reaching  its  maximum  of  intensity 
towards  the  time  of  New  Moon,  when  it  covered 
all  the  face  and  chest  and  caused  unbearable  irrita- 
tion. After  this  epoch  all  the  symptoms  gradually 
disappeared,  and  the  face  became  clear,  but  the 
same  symptoms  were  seen  to  begin  again  as  soon 
as  the  Full  Moon  had  passed. 


ACTION   ON   MEN   AND   ANIMALS     175 

In  another  disease  of  this  class  the  same  doctor 
noticed  that  a  similar  series  of  phenomena  appeared 
in  a  reversed  order. 

Whatever  be  the  opinion  one  may  profess  on 
the  mechanism  of  the  development  of  such  maladies, 
it  would  not  be  absurd  to  compare  them  to  those 
nervous  phenomena  that  to  a  certain  degree  are 
dependent  on  lunar  influences.  Mead  has  cited  the 
case  of  a  child  that  always  suffered  from  convulsions 
at  the  time  of  the  Full  Moon,  and  Piso  observed 
that  an  attack  of  paralysis  recurred  with  every  New 
Moon,  that  is  to  say,  at  the  periods  of  least  activity. 

According  to  Menuret,  with  some  epileptics  the 
attacks  recur  at  the  moment  of  the  Full  Moon. 

One  does  not  at  first  sight  see  very  well  how 
our  satellite  can  act  in  such  a  way,  but  we  may  at 
least  point  out  that  all  nervous  maladies,  and  in 
certain  cases  those  that  affect  the  terminations  of 
the  nerves  in  certain  skin  diseases,  appear  to  be 
directly  dependent  on  electrical  influences.  Now, 
there  can  be  no  doubt  that,  especially  in  the  higher 
regions  of  the  atmosphere,  the  charge  of  atmo- 
spheric electricity  can  vary  under  the  influence  of 
the  Moon's  light,  and  one  might,  strictly  speaking, 
connect  the  two  kinds  of  phenomena. 


i y6  A   DAY   IN   THE   MOON 

What  further  appears  to  corroborate  these  some- 
what daring  views  is  the  mass  of  organic  facts 
observed  long  since  in  hospitals  in  the  cases  of 
patients  suffering  clearly  and  exclusively  from 
nervous  troubles — vertigo,  hysteria,  somnambulism, 
etc. — in  a  way  more  or  less  in  relation  with  the 
phases  of  the  Moon. 

This  was  the  opinion  of  the  celebrated  Gall,  who 
declared  that  he  had  recorded,  in  the  case  of  weakly 
persons,  two  epochs  of  irritability  corresponding  to 
the  New  Moon  and  the  Full  Moon. 

The  celebrated  physician  and  astronomer  Olbers 
attempted  to  make  an  experimental  verification  of 
these  facts,  and  after  having  been  long  in  medical 
practice,  he  denied  them  all  absolutely. 

Those  who  are  of  the  opposite  opinion  object  to 
this  way  of  looking  at  the  matter  that  the  instances 
observed  in  our  countries  are  much  less  numerous 
than  those  of  tropical  lands. 

But  however  this  may  be,  Balfour  felt  satisfied 
that  in  Bengal  the  progress  of  certain  maladies,  and 
particularly  that  of  intermittent  fevers,  follows  the 
course  of  the  Moon. 

Bruce  asserts  that  more  than  once  he  observed 
that  the  Moon  exercises  such  an  influence  on 


ACTION   ON   MEN   AND   ANIMALS    177 

epileptics,  and  with  such  regularity  that  it  is 
always  on  the  third  day  of  the  Full  Moon  that 
the  paroxysm  of  the  illness  ended  in  an  intermittent 
fever. 

It  was,  besides,  a  generally  received  opinion  among 
Orientals  that  epileptics  were  agitated  by  the  Moon, 
and  it  was  on  account  of  this  opinion  that  they 
were  given  the  name  of  lunatics,  a  term  after- 
wards applied  to  the  insane. 

The  observations  of  Fontana  bearing  on  the  same 
subject  were  also  made  in  hot  countries,  but  the 
case  that  most  clearly  points  to  lunar  influence  is 
that  reported  in  the  first  volume  of  the  Memoirs 
of  the  Royal  Academy  of  Madrid.  The  patient  in 
question  was  attacked  periodically  with  a  difficulty 
of  breathing,  which  became  more  marked  at  the 
approach  of  New  and  Full  Moon. 

This  singular  illness  lasted  for  several  years  in 
succession. 

It  is   probably   to   the   fewness  of  such   observa- 
tions  in   the  hospitals  of  France  and  Europe   that 
one    must    attribute    the    opinion    of    pathologists, 
who   are   little   disposed   to   accept    the    theory    of 
lunar  influences  on  their  patients. 

Nevertheless  it  is  the  opinion  of  several  alienists 
12 


iy8  A   DAY   IN   THE   MOON 

of  our  own  day  that  their  patients  are  more 
agitated  at  the  period  of  the  Full  Moon  than  at 
that  of  New  Moon. 

It  might  be  well  to  take  up  the  question 
again  both  here  at  home  and  in  our  tropical 
possessions. 

It  would  be  a  fine  subject  for  a  thesis  for  the 
doctor's  degree  for  such  of  my  pupils  as  are  short 
of  suggestions  or  of  material. 

Experience  alone  can  decide  the  question.  What 
we  must,  however,  insist  upon  is  that  our  organism 
is  infinitely  more  sensitive  to  outside  influences 
than  much  of  the  apparatus  invented  by  modern 
physicists,  and  that,  besides,  the  human  body  must 
be  a  receiver  for  wonderfully  synchronised  waves 
of  radiations  still  unknown  to  us  ;  that  we  have 
an  electric  or  magnetic  sense,  which  permits  us 
to  perceive  variations  of  this  kind,  though  of 
infinitesimal  amount ;  and  that  the  learned  men  of 
our  day,  when  they  talk  of  "  nervous  influx,"  are 
hiding  under  this  term  their  profound  ignorance 
of  the  mechanism  that  regulates  all  our  organic 
actions. 

We  conclude  that  we  should  continually  study 
matters,  and  not  rashly  cast  aside  the  opinions  of 


ACTION   ON    MEN   AND  ANIMALS    179 

our  ancestors,  especially  when  we  find  them 
supported  by  facts  of  which  the  authenticity  cannot 
be  called  in  question. 

The  Moon,  that  great  satellite,  so  near  our 
earth,  which  from  the  mechanical  point  of  view 
causes  such  enormous  perturbations  to  our  world, 
should  not  be  treated  as  a  negligible  factor  from 
whatever  point  of  view  we  consider  it. 

There  seems  no  doubt  about  its  having  some 
influence  on  life,  but  to  what  degree  is  this 
exerted  ?  That  is  the  new  question  that  appeals 
to  learned  and  ignorant,  physicist  and  physician, 
physiologist  and  astronomer. 

These  serious  considerations  are,  it  seems  to  me, 
calculated  to  restore  to  their  due  place  certain 
branches  of  lunar  research,  which  have  been  too 
much  neglected  by  students  of  the  heavens. 
Perhaps  they  will,  moreover,  avail  to  merit  for  me 
the  forgiveness  of  the  astrologers,  of  whom  I  have 
said  so  many  hard  things  in  the  course  of  this 

work. 

*  *  *  *  * 

It  is  not  generally  known  that  the  study  of 
the  Moon  is  within  the  reach  of  low-powered  in- 
struments. 


i8o  A   DAY   IN   THE   MOON 

One  need  only  have  a  comparatively  small  tele- 
scope to  make  very  interesting  observations. 

We  have  seen  that  many  selenographers  had  at 
their  disposal  only  instruments  of  small  aperture 
and  short  focal  distance.  They  have,  all  the  same, 
done  useful  work  in  exploring  the  surface  of  our 
satellite. 

Why  should  not  a  good  many  of  my  readers 
do  the  same. 

And  here  one  must  take  care  not  to  fall  into 
a  very  widespread  error.  When  one  sets  about 
the  study  of  Physical  Astronomy  one  imagines  that 
one  will  see  much  better  by  using  high  magnifying 
powers.  It  is  a  great  mistake. 

With  telescopes  of  low  power,  objects  are  always 
seen  very  sharply  defined,  and  it  is  thus  one  should 
begin  to  observe. 

First  of  all,  train  your  eyes ;  the  faculty  of 
penetrating  vision  will  come  later. 

It  is  rather  a  long  task,  but  the  trouble  is  well 
repaid. 

Throughout  you  will  be  able  to  see  enough  of 
detail  to  take  a  great  interest  in  it,  and  so  much 
that  you  will  be  embarrassed  when  you  have  to 
reproduce  what  you  see  in  a  sketch. 


ACTION   ON   MEN   AND   ANIMALS    181 

Since  the  application  of  photography  to  the 
study  of  the  Moon,  there  has  been  too  much 
neglect  of  direct  vision  and  the  study  of  detail ; 
this  should  be  taken  up  again,  unless  we  are 
merely  to  mark  time  and  make  no  progress. 

Lunar  photographs  are  useful  in  the  sense  that 
they  fix  the  topography  of  our  satellite  in  a 
definite  way,  better  than  this  can  be  done  by 
micrometer  measurements.  But  when  it  comes  to 
observing  fissures,  small  craters,  passing  shadows, 
and  elevations  of  no  great  height,  nothing  is 
equal  to  direct  observation  with  the  eye. 

A  telescope  of  108  millimetres  shows  far  more 
objects  than  the  best  photographs. 

Finally,  there  are  regions  which  should  be 
specially  studied.  They  are  those  that  present 
certain  curious  peculiarities  from  the  geological 
and  volcanic  point  of  view  ;  others  may  be  recom- 
mended by  their  picturesque  character,  as,  for 
instance,  the  "  Straight  Range "  of  the  Moon,  of 
which  we  have  already  spoken,  or  the  famous 
woman's  head  in  the  Moon  so  well  known  to  the 
old  selenographers. 

In  his  first  maps  Cassini  had,  in  fact,  drawn 
at  the  western  end  of  the  "  Sinus  Iridum "  the 


1 82  A   DAY    IN   THE    MOON 

promontory  of  the  Heraclides  in  the  form  of  the 
head  of  a  young  woman.  It  was  long  believed 
that  the  famous  astronomer  merely  intended  by 
this  means  to  distinguish  his  map  from  those  that 
preceded  it,  and  thus  to  sign  it,  so  to  say. 

And  it  was  not  till  long  after  that  this  strange 
appearance  was  again  seen.  In  the  drawing  of 
Schroeter  the  form  shown  by  Cassini  is  not  to 
be  recognised.  That  of  M.  Mabire  gives  it,  how- 
ever, but  with  the  appearance  of  an  aged  woman. 

One  evening,  when  I  was  studying  the  Moon, 
I  saw  the  same  promontory  once  more  under 
a  form  very  like  that  in  Cassini's  drawings.  The 
apparition  with  its  extended  wings  looked  rather 
like  a  nymph  or  a  na'iad. 

There  is  really  here,  then,  a  mere  question  of 
lighting.  When  closely  surveying  the  surface  of 
the  Moon,  it  sometimes  happens  that  one  grasps 
details  that  only  present  themselves  on  rare 
occasions,  as  the  result  of  libration  varying  to  an 
endless  extent  the  angle  at  which  the  solar  rays 
fall. 

One  can  also  with  the  help  of  a  telescope  of 
low  power  secure  interesting  photographs  of  our 
satellite. 


ACTION   ON    MEN   AND   ANIMALS    183 

As  is  well  known,  all  that  is  necessary  is  to 
replace  the  ordinary  eye-piece  by  that  of  the 
instrument,  or,  better  still,  fit  the  camera  to  the 
telescope,  leaving  the  eye-piece  in  position. 

In  an  instrument  of  small  aperture  the  difference 
between  the  optical  and  chemical  focus  is  almost 
inappreciable,  and  one  soon  succeeds  in  finding 
the  right  position  after  a  few  trials. 

This  method  is  of  the  greatest  service  when  it 
is  a  matter  of  photographing  the  phases  of  an 
eclipse  of  the  Moon  or  the  Sun,  and  I  have  often 
used  it  successfully  on  these  occasions.  An 
exposure  of  a  fraction  of  a  second  gives  excellent 
results. 

With  these  practical  hints  I  close  the  volume. 
I  shall  be  happy  if  I  have  succeeded  in  developing 
in  some  of  my  readers  a  taste  for  those  lunar 
studies  that  are  within  the  reach  of  anyone  who  is 
in  earnest  about  them. 


LIST   OF   348   OBJECTS   SHOWN   ON   THE 

MAP   OF   THE   MOON,   DRAWN   BY 

THE   ABfi£    MOREUX 

(CRATERS,  MOUNTAINS,  AND   INEQUALITIES 
OF   THE   SURFACE) 


The  letters  N.E.,  S.E.,  N.W.t  S.W.,  signify  North-east,  South-east, 
North-west,  South-west,  and  indicate  in  -which  quarter  oj  the  Moon 
the  objects  art  to  be  sought  for. 


S.W. 
N.W. 
N.W. 
N.W. 

N.E. 

N.W. 

S.W. 

N.E. 

N.W. 

N.W. 

S.E. 

N.W. 

N.W. 

S.W. 

N.W. 

S.W. 
S.E. 


Abenezra 

S.W. 

Apian  . 

Abulfeda 

S.W. 

Apollo 

JEnarium  (promontory) 

S.E. 

Arago  . 

Agatharchides 

S.E. 

Aratus 

Agrippa 

N.W. 

Archimedes 

Airy     . 

S.W. 

Archytas 

Albategnius 

S.W. 

Argelander  . 

Alexander    .         .         . 

S.W. 

Ari  starch  us  . 

Alhazen 

N.W. 

Aristillus 

Almanon 

S.W. 

Aristotle 

Alpetrages    . 

S.E. 

Arzachel 

Alps  (Mts.)  . 

South 

Atlas    . 

Alps  (Valley  of)   . 

S.W. 

Autolycus    . 

Altai  (Mts.) 

S.W. 

Azophi 

Anaximander 

N.E. 

Azout  . 

Anaximenes 

N.E. 

Ansgar 

S.W. 

Bacon  . 

Apennines  (Mts.) 

N.E. 

Bailly  . 

184 


OBJECTS   ON    MAP   OF    MOON       185 


Baily  . 

.  S.W. 

Cardan 

.  N.E. 

Ball     .       ,». 

.  S.E. 

Carlini 

.  N.E. 

Barocius      .        . 

.  S.W. 

Carpathians  (Mts.) 

.  N.E. 

Bayer  .         .        . 

.  S.E. 

Cassini         .        . 

.  N.W. 

Beaumont    . 

.  S.W. 

Catherine     .         . 

.  S.W. 

Behaim 

.  S.W. 

Caucasus  (Mts.)  . 

.  N.W. 

Berosus 

.  N.W. 

Cavendish    . 

.  S.E. 

Bessarion     .         . 

.  N.E. 

Cepheus       .         . 

.  N.W. 

Bessel          . 

.  N.W. 

Chacornac  . 

.  N.W. 

Bianchini     . 

.  N.E. 

Chevallier    .        .• 

.  N.W. 

Biela    .        .  ' 

.  S.W. 

Cichus.        .        . 

.  S.E. 

Birt     . 

.  S.E. 

Clairaut        . 

.  S.W. 

Boguslawski      -  . 

.  S.W. 

Clavius         ,        . 

.  S.W. 

Bohnenberger 

.  S.W. 

Cleomedes  .        -. 

.  N.W. 

Bond  . 

.  S.W. 

Colombo      .        . 

.  S.W. 

Bonpland     . 

.  S.E. 

Condamine  .       :. 

.  N.E. 

Borda  . 

.  S.W. 

Condorcet   .        . 

.  N.W. 

Boscovitch  . 

.  N.W. 

Cook  .        .        „ 

.  S.W. 

Bouguer 

.  N.E. 

Copernicus  .        . 

.  N.E. 

Boulliaud     . 

.  S.E. 

Cruger         . 

.  S.E. 

Boussingault 

.  S.W. 

Curtius 

.  S.W. 

Bouvard 

.  S.E. 

Cuvier. 

.  S.W. 

Bradley  (Mts.)     . 

.  N.W. 

Cyrillus        .       ..- 

.  S.W. 

Briggs.      ^  ,  .      . 

.  N.E. 

Cysatus 

.  S.W. 

Buch  . 

.  S.W. 

Burckhardt  . 

.  N.W. 

D'Alembert  (Mts.) 

.  S.E. 

Burg    . 

.  N.W. 

Damoiseau  . 

.  S.E. 

Busching     . 

.  S.W. 

Davy  . 

.  S.E. 

Dawes         .         • 

.  N.W. 

Calippus      . 

.  N.W. 

Delambre    . 

.  S.W. 

Campanus   .         . 

.  S.E. 

De  la  Rue  . 

.  N.W. 

Canon          .         .-- 

.  N.W. 

Delisle 

.  N.E. 

Capella 

.  S.W. 

Democritus  .         . 

.  N.W. 

Capuanus    . 

.  S.E. 

Descartes     .       •  •  •'. 

.  S.W. 

i86 


A   DAY   IN   THE   MOON 


Diophantes  . 

.  N.E. 

Gauss  . 

.  N.W. 

Doerfel  (Mts.) 

.  S.E. 

Gay-Lussac  . 

.  N.E. 

Donati 

.  S.W. 

Geminus 

.  N.W. 

Doppelmayer 

.  S.E. 

Gerard 

.  N.E. 

Drebbel       . 

.  S.E. 

Goclenius     . 

.  S.W. 

Godin  . 

.  N.W. 

Egede 

.  N.W. 

Grimaldi 

.  S.E. 

Eichstadt     . 

.  S.E. 

Gruemberger 

.  S.E. 

Eimmart 

.  N.W. 

Gruithuisen 

.  N.E. 

Encke 

.  N.E. 

Guerike 

.  N.E. 

Endymion  . 

.  N.W. 

Guttenberg  . 

.  S.W. 

Eratosthenes 

.  N.E. 

Euclid 

.  S.E. 

Hadley  (Mts.)      . 

.  S.W. 

Eudoxus 

.  N.W. 

Rasmus  (Mts.) 

.  N.W. 

Hagecius 

.  s.w. 

Fabricius 

.  s.w. 

Hainzell 

.  S.E. 

Fermat 

.  s.w. 

Halley 

.  S.W. 

Fernel 

.  s.w. 

Halm  . 

.  N.W. 

Firmicus 

.  N.W. 

Hansen 

.  N.W. 

Flamsteed   . 

.  S.E. 

Hansteen     . 

.  S.E. 

Fontana 

.  S.E. 

Harbinger   . 

.  N.E. 

Fontenelle  . 

.  N.E. 

Harding 

.  N.E. 

Fourier 

.  S.E. 

Harpalus 

.  N.E. 

Fournier 

.  S.W. 

Hecatseus    . 

.  S.W. 

Fracastorius 

.  S.W. 

Heinsius 

.  S.E. 

Fra  Mauro  . 

.  S.E. 

Helicon 

.  N.E. 

Franklin      % 

.  N.W. 

Hell    . 

.  S.E. 

Fraunhofer  . 

.  S.W. 

Hercules 

.  N.E. 

Frisius  (Gemma)  . 

.  S.W. 

Hercynian  (Mts.) 

.  S.E. 

Herigonius  . 

.  S.E. 

Galileo 

.  N.E. 

Herodotus  . 

.  N.E. 

Gambart 

.  N.E. 

Herschel 

.  N.E. 

Gartner 

.  N.W. 

Herschel,  C. 

.  N.E. 

Gauricus 

.  S.E. 

Herschel,  J. 

.  N.E. 

OBJECTS   ON   MAP   OF    MOON       187 


Hesiod 

.  N.E. 

Leibnitz  (Mts.)    . 

.  S.W. 

Hevelius 

.  N.E. 

Lemonnier  . 

.  N.W. 

Hind  . 

.  s.w. 

Letronne 

.  S.E. 

Hipparchus  . 

.  S.W. 

Leverrier 

.  N.E. 

Hypatia 

.  s.w. 

Lexell 

.  S.E. 

Licetus 

.  S.W. 

Inghirami    . 

.  S.E. 

Lichtenberg 

.  N.E. 

Isidore 

.  S.W. 

Lilius  . 

.  S.W. 

Lindenau     . 

.  S.W. 

Jacobi 

.  s.w. 

Linnee 

.  N.W. 

Janssen 

.  N.W. 

Longomontanus  . 

.  S.E. 

Julius  Caesar 

.  N.W. 

Lubiniezky  . 

.  S.E. 

Kant    . 

.  S.W. 

Maclaurin    . 

.  S.W. 

Kastner 

.  S.W. 

Maclear 

.  N.W. 

Kepler 

.  N.E. 

Macrobius   . 

.  N.W. 

Kies    . 

.  S.E. 

Mairan 

.  N.E. 

Kirch  . 

.  N.E. 

Manginus     . 

.  S.E. 

Kircher 

.  S.E. 

Manilius 

.  N.W. 

Kraft  . 

.  N.E. 

Manzinus    , 

.  S.W. 

Kunowsky   . 

.  N.E. 

Maraldi 

.  N.W. 

Marinus 

.  S.W. 

Lacroix 

.  S.E. 

Marius 

.  N.E. 

Lagrange 

.  S.E. 

Maskelyne  . 

.  N.W. 

Lagrenus 

.  S.W. 

Maurolycus  . 

.  S.W. 

Lahire 

.  N.E. 

Mayer,  Ch.  . 

.  N.W. 

Lalande 

.  S.E. 

Menelaus     . 

.  N.W. 

Lambert 

.  N.E. 

Mercator 

.  S.E. 

Landsberg   . 

.  S.E. 

Mercury 

.  N.W. 

Lapeyrouse  . 

.  S.W. 

Mersenne    . 

.  S.E. 

Lassell 

.  S.E. 

Messier 

.  S.W, 

Lavoisier     . 

.  N.E. 

Milichius 

.  N.E. 

Legendre     . 

.  S.W. 

Miller  . 

.  S.E. 

Lehmann     . 

.  S.E. 

Moigno 

.  N.W. 

i88 


A   DAY    IN   THE   MOON 


Hosting 
Murus  rectus 

.  S.E. 
.  S.E. 

Posidonius  . 
Proclus 

.  N.W. 
.  N.W. 

Mutus 

.  S.W. 

Prom.  Heraclides 

.  N.E. 

Nasireddin  . 
Neander 
Ne'per  . 
Nicolai 

.  S.E. 
.  S.W. 
.  N.W. 
.  S.W. 

Prom.  Laplace     . 
Ptolemy 
Pyth  agora    . 
Pytheas 

.  N.E. 
.  S.E. 
.  N.E. 
.  N.E. 

Nicollet 

.  S.E. 

Rabby 
Ramsden     . 

.  S.W. 
.  S.E. 

CErsted 

.  N.W. 

Reichenbach 

.  S.W. 

Oken  . 

.  S.W. 

Reiner 

.  N.E. 

Oriani  . 

.  N.W. 

Reinhold     , 

.  N.E. 

Pallas  . 

.  N.E. 

Repsold 
Rhseticus 

.  N.E. 

.  N.W. 

Pentland 

.  S.W. 

Rheita 

.  S.W. 

Petavius 

.  S.W. 

Ricci  . 

.  S.W. 

Philolaus 

.  N.E. 

Riccioli 

.  S.E. 

Phocylides  . 
Piazzi  . 

.  S.E. 
.  N.E. 

Riphsean  Mountains 
Ritter  . 

.  S.E. 
.  N.W. 

Picard 

.  N.W. 

Rocca 

.  S.E. 

Piccolomini 

.  S.W. 

Roemer 

.  N.W. 

Pico    . 
Pictet  . 
Pitatus 

.  N.E. 
.  S.E. 
.  S.E. 

Rook  (Mts.) 
Rosenberger 
Ross    . 

.  S.E. 
.  S.W. 

.  N.W. 

Pitiscus      V 

.  S.W. 

Rost    . 

.  S.E. 

Plana  .    •'  .  fa  '    '. 

.  N.W. 

Plato  . 

.  N.E. 

Sabine 

.  N.W. 

Playfair 
Pliny  . 
Plutarch 

.  S.W. 

.  N.W. 
.  N.W. 

Sacrobosco  . 
Santbech 
Sasseride 

.  S.W. 
.  S.W. 
.  S.E. 

Polybius 
Pontanus 

.  S.W. 
.  S.W. 

Saussure 
Scheiner 

.  S.E. 
.  S.E. 

Pont6coulant 

.  S.W. 

Schiaparelli 

.  N.E. 

OBJECTS   ON   MAP   OF   MOON       189 


Schickard    . 

.  S.E. 

Timaeus 

.  N.E. 

Schiller        .        ..- 

.  S.E. 

Timocharis  . 

.  N.E. 

Schrieter      .         . 

.  N.E. 

Tobias  Mayer 

.  N.E. 

Schubert 

.  N.W. 

Torricelli     .        . 

.  S.W. 

Secchi 

.  N.W. 

Trallus         . 

.  N.W. 

Segner 

.  S.E. 

Tries  necker          .  ; 

.  N.W. 

Seleucus 

.  N.E. 

Tycho          .         . 

.  S.E. 

Sharp  . 

.  N.E. 

Short  . 

.  S.E. 

Ukert  . 

.  N.W. 

Snellius        .        . 

.  S.W. 

Ulugh  Bey  . 

.  N.E. 

Sommering  .        . 

.  N.W. 

Sosigenes     .         . 

.  N.W. 

Vega   . 

.  S.W. 

South  . 

.  N.E. 

Vendelinus  . 

.  S.W. 

Stadius        .        * 

.  N.E. 

Vieta  . 

.  S.E. 

Steinheil      .        . 

.  S.W. 

Vitello 

.  S.E. 

Stevin  . 

.  S.W. 

Vitruvius     . 

.  N.W. 

Stiborius      .    :     . 

.  S.W. 

Vlacq  . 

.  S.W. 

Stoefler 

.  S.W. 

Strabo 

.  N.W. 

Walter 

.  S.E. 

Straight  Range     . 

.  N.E. 

Webb.         .         . 

.  S.W. 

Street  .         .         . 

.  S.E. 

Weigel         .         . 

.  S.E. 

Struve          . 

.  N.E. 

Werner        .        , 

.  S.W. 

Wichmann  . 

.  S.E. 

Taruntius     .         . 

.  N.W. 

Wilhelm  I.  .        . 

.  S.E. 

Taurus  (Mts.) 

.  N.W. 

Wolf  (Mts.) 

.  N.E. 

Taylor 

.  S.W. 

Wurzelbauer 

.  S.E. 

Thales 

.  N.W. 

Theataetus   . 

.  N.W. 

Zagut  .         ,         . 

.  S.W. 

Thebit 

.  S.E. 

Zuchius        .        . 

.  S.E. 

Theophilus  . 

.  S.W. 

Zupus  .     .  _.-.      . 

.  S.E. 

OBJECTS   TO   BE    STUDIED    ON    EACH    DAY 
OF  THE   LUNATION 

znd  Day. — Mare  Crisium. — Messala. — Sunrise  on  the  Sea  of 
Humboldt. — Langrenus,  Vendelinus,  Condorcet, 
Hansen,  Gauss,  Hahn,  Berosus. 

yd  Day. — Craters  in  the  Mare  Crisium. — Taruntius,  Picard, 
Fraunhofer,  Vega,  Pontecoulant,  Cleomedes, 
Fournier,  Petavius,  Endyraion,  Messier,  Vlacq. 

tfh  Day. — Mare  Nectaris. — Macrobius,  Proclus. — Sunrise  on 
Fracastorius,  Rheita,  and  Maetius,  with  the  valley 
that  separates  them. — Guttenberg,  Colombo,  Sant- 
bech,  the  mountain  region  to  the  west  of  the 
Mare  Serenetatis,  Hercules,  Atlas. 

$th  Day. — "Marsh  of  Sleep,"  Plana,  Capella,  Isidore,  Polybius, 
Piccolomini,  Vitruvius,  Littrow,  Fabricius,  Posi- 
donius,  Lemonnier,  Theophilus,  Cyril,  Catherine. 

6th  Day. — Tacitus,  Maurolycus,  Barocius,  Dionysius,  Sosi- 
genes,  Abulfeda,  Descartes,  Almanon,  Gemma 
Frisius,  Pliny,  Ross,  Arago,  Delambre,  Aristotle, 
Eudoxus,  Julius  Caesar,  Linnaeus,  M£nelas. 

1th  Day. — Ptolemy,  Albategnius,  Manilius,  Hyginus  and  its 
rills,  Hipparchus,  Autolycus,  Aritillus,  Cassini, 
Valley  of  the  Alps,  W.  C.  Bond,  Walter,  Miller, 
Lacaille,  Apennines,  Triesnecker  and  its  rays. 

%th  Day. — Mare  Frigoris,  Arzachel,  Alphonso,  Alpetagrius, 
Bode,  Pallas,  Archimedes,  Plato,  Maginus, 
Moesting,  Thebit,  Murus  Rectus,  Saussure,  Morel, 
Lalande,  Kirch. 

190 


OBJECTS  TO  STUDY  EACH  DAY      191 

f)tk  Day. — Tycho,  Clavius,  Eratosthenes,  Stadius,  Timocharis, 
Pitatus,  Gruemberger,  Mountains  of  Teneriffe, 
region  to  the  west  of  Fontenelle,  Gambart. 

loth  Day. — Sinus  Iridium,  Copernicus,  Hesiod  and  the  fissure 
to  the  east  of  it,  Wilhelm  I,  Longomontanus, 
Heinsius,  Pytheas,  Lambert,  Helicon,  Wurzel- 
bauer. 

nth  Day. — Boulliaud,  Campanus,  Mercator,  Reinhold, 
Riphsean  Mountains,  Hippalus,  Capuanus,  Blan- 
canus,  Tobias  Mayer. 

i.2th  Day. — Mare  Imbrium,  Gassendi,  Aristarchus,  Herodotus, 
Marius,  Flamsteed,  Schiller,  Mersenne,  Doppel- 
mayer. 

\^th  Day. — Schickard, Wargentin,  Grimaldi,  Hevelius, Seleucus, 
Cruger,  Briggs. 

i^th  Day. — Smith's  Sea,  Bouvard,  Riccioli,  Hercynian  Moun- 
tains, Cardan,  Cordilleras,  Pythagoras. 


LUNAR   ELEMENTS 


According  to 
Elger. 

According  to 
the  Author. 

Mean  apparent  diameter 

3i'  8" 

31'  3-26" 

Maximum  apparent  diameter  . 

33'  33'2o" 

— 

Minimum  apparent  diameter  . 

29'  23-65" 

— 

Real  diameter  in  miles  . 

2,160 

Volume   (that   of    the   Earth\ 
being  i).                               / 

Mass  (that  of  the  Earth  being  i  ){ 

i 

0^0204 
I 

or  o  02033 
49  2 

o  01  28  or  0 
8i'4 

81-5 

Density  compared  to  the  Earth 

0-60419 

o'6i 

Density  compared  to  water     . 

3  '444 

3'42 

Extent  of  surface    . 

14,657,402  sq.  miles 

Surface  of  the  Earth 

197,000,000  sq.  miles 

Surface  of  the  Earth  being  i,"l 
that  of  the  Moon.                 / 

Force  of  gravity  at  the  surface-! 

—  or  abou 
27 

r\f  fKrt*- 

t  0^07407 

i 
~6~ 

6-065 
on  the  Earth 

Proportion  of  surface  of  the) 
Moon  that  is  never  visible.  J 

0*4100 

— 

Surface  of  the  Moon  seen  at\ 
at  one  time  or  another.        / 

0*5900 

— 

192 

'93 


According  to 
Elger. 

According  to 
the  Author. 

Synodic  month,  or  interval  V 
from  one  New  Moon  to  the  I 
following  New  Moon  (luna-j 
tion).  J 

Sidereal  month,  or  interval  of 
time  between  two  successive 
passages  in  front  of  the  same 
star. 

Tropical  month,  or  intervah 
between  two  successive  pas- 1 
sages  of  the  point  Gamma  j 

(y).  J 

Anomalistic  month,  or  inter-'i 
val   between   two   passages 
through  perigree.  J 

Nodical  month,  or  interval] 
between  two  passages  of  the  j- 
ascending  node. 

Mean  distance  in  terms  ofi 
the  Earth's  radius  at  the 
Equator.  J 

Mean  distance  in  miles  . 
Maximum  distance 
Minimum  distance 
Mean  excentricity  of  orbit 

Mean  inclination  of  the  orbit  \ 
of  the  Moon  to  the  Ecliptic./ 

Inclination  of  the  axis  of  the} 
Moon  to  the  Ecliptic.  / 

Inclination  of  the  Moon's^ 
equator  to  the  Ecliptic.  J 

Maximum  libration  in  latitude 
13 


29  days  12  hr.  44  min. 

2*684  sec.,  or 
29'53°5887  days 

27  days  7  hr.  43  min, 

1 1  -545  sec.,  or 
27-3216614  days 

27  days  7  hr.  43  min. 

4'68  sec.,  or 

27-321582  days 

27  days  13  hr.  18  min. 
37-44  sec.,  or 
2  7 '5  5  460  days 

27  days  5  hr.  5  min. 
35 '8 1  sec.,  or 
27*21222  days 

60-27 

238,840 
252,972 
221,641 

0*05490807 

5°  8'  39-96" 

87°  27' 5i" 

1°  32'  9" 
60°  44' 


'94 


A  DAY   IN  THE   MOON 


According  to 
Elger. 

According  to 
the  Author. 

Maximum  libration  in  lon-^ 
gitude.  / 

Maximum  total  libration  aO 
the  centre  of  the  Earth.  J 

Maximum  diurnal  libration    . 

Angle  subtended  by  a  degree 
of  lunar  latitude  and  longi- 
tude in  the  centre  of  the 
Moon's  disc  at  mean  dis- 
tance. 

Length  of  a  degree  in  these  1 
conditions.  / 

Lunar  arc  at  the  centre  of  the-| 
Moon's  surface  subtending/ 
an  angle  of  a  second  of  arc.J 

Period  of  like  phase 
Or  more  exactly     . 


7ou  45 

10°  1 6' 
i°  i'  28-8" 

16-566* 
18-97715  miles 


59  days  i  hr.  28min. 
2  lunations 

442  days  23  hr.  = 
15  lunations 


On  our  English  maps  and  diagrams  of  the  Moon  the  old 
Latin  forms  of  the  names  of  lunar  "seas  "  are  generally  used. 
In  the  following  list  some  of  the  chief  of  these  are  given,  with 
the  corresponding  English  meaning  : — 


Mare  Tranquillitatis 
Mare  Foecunditatis   . 
Mare  Serenitatis 
Mare  Crisium    . 
Mare  Frigoris   . 
Mare  Vaporum 
Mare  Imbrium 
Mare  Nubium  . 
Mare  Humorum 
Mare  Nectaris  . 
Mare  Australis 
Oceanus  Procellarum 
Lacus  Mortis    .     :    . 
Lacus  Somniorum     . 
Sinus  Iridum     . 
Sinus  Rons 


Sea  of  Tranquillity 
Sea  of  Fecundity 
Sea  of  Serenity 
Sea  of  Crises 
Sea  of  Cold 
Sea  of  Vapours 
Sea  of  Rains 
Sea  of  Clouds 
Sea  of  Humours 
Sea  of  Nectar 
Southern  Sea 
Ocean  of  Tempests 
Lake  of  Death 
Lake  of  Dreams 
Gulf  of  Rainbows 
Gulf  of  Dew 


195 


CHIEF   CHAINS   OF   LUNAR   MOUNTAINS 


Name. 

Greatest  height. 
Feet. 

Length. 
Miles. 

Alps   .          .          . 

10,760 



Caucasus    ..... 

18,700 

— 

Apennines  ..... 

19,600 

400 

Carpathians         .... 

6,500 

1  80 

Chain  of  the  Sinus  Iridium  . 

13,280 

312 

Taurus  Mountains 

9,840 

— 

Teneriffe  Mountains   . 

7,870 

— 

Harbinger  Mountains 

6,890 

— 

Hercynian  Mountains 

8,200 

— 

Pyrenees     .         .         .         . 

1  1,  800 

190 

Altai'  Mountains  .... 

12,790 

276 

Riphaean  Mountains    . 

2,95° 

IOO 

Percy  Mountains 

— 

— 

Leibnitz  Mountains     . 

25.S90 

— 

Doerfel  Mountains 

25.590 

— 

Rook  Mountains 

24,600 

— 

D'Alembert  Mountains 

19,680 



196 


INDEX 

In    the   following  Index    the    names    of    objects   in  the  Moon 
(mountains,  seas,  etc.)  are  printed  in  italics. 


Achilles  Tatius,  9 

Albergotti,  theory  of  the  Moon, 

35 
Albertus  Magnus  (description  of 

the  Moon  by),  31 
Alexandria,  pharos  of,  25 
Alphonso,  115 
Alps,  lunar,  no 
Apennines,  lunar,  109 
Arago,  59 
Archimedes,  no 
Archimedes,     use     of     concave 

mirrors  by,  24 
Aristarchus   on   the   phases    of 

the  Moon,  34 
Aristotle,  9 
Arzachel,  115 
Astrology,   153 
Ayme  (Henri),  on  alleged  lunar 

influence  on  vegetation,  140 

Beer  and  Midler's  map,  62,  63 
Berosus,  his  theory  of  the  Moon's 

phases,  34 
Birt,   115 

Boulainvilliers,  167 
Brewster,  23 
Bruce,  176 
Buffon,  25,  176 


Carbonnier,      experiments      on 
cryptogamic  vegetation,   151 


Cardan,  Jerome,  158 

Carpenter.     See  Nasmyth 

Cassini,  58,  181,  182 

Catharine  de'  Medici,  162,  etc. 

Charbonneaux,  in 

Charles  VI,  173 

Charles  IX,  162 

Clavius,  88,  116 

Colonna,  167 

Copernicus,  83,  87,  92,.  103,  108, 

114 
Cordier     and     Compiegne,     on 

lunar   action   on    vegetation, 

147 
Cyrano  de  Bergerac,  67,  69 

Delattre,  discoveries  on  the  site 

of  Carthage,  22 
Democritus,  theory  of  the  Milky 

Way,  24 

Doerf el  Mountains,  116 
Dulaure,  163 

Edward  VI,  158 
Elger,  64 
Eratosthenes,  109 
Euler,  44 

Fontana,  177 
Franz,  117 

Galeotti  (astrologer),  156 


197 


198 


INDEX 


Galileo's  discovery  of  the  tele- 
scope, 10  ;  his  first  picture  of 
the  Moon,  14  ;  his  methods 
of  argument,  35,  123,  124 

Gall,  176 

Galle-Defond,  on  alleged  action 
of  the  Moon  on  vegetation, 
145  ;  and  on  animal  life,  172 

Gassendi,  167 

Gaudibert,  64 

Gauss,  87 

Goodacre's  map,  64 

Grimaldi,  88 

Gruithuisen,  62 

Henri  II,  162 
Henri  III,  161 
Heraclides,  182 
Herschel,  59,  60 
Herschel,  87 
Hevelius,  54 
Hipparchus,  115 
Huggins,  in 
Humboldt,  88 
Huyghens,  no 
Hyginus,  114 

Jacques,  on  lunar  influence  on 

tropical  vegetation,  149 
Joubert,  174 

Kepler,  54,  123,  160,  161 
Kepler,  114 
Kolbe,  74 

Krosigk,  Baron,  researches  on 
distance  of  the  Moon,  74 

Lacaille,  74 

Lagrange,  87 

La  Hire's  lunar  globe,  59 

Lalande,  74,  168 

Langrenus   (Van  Langren),   his 

map  of  the  Moon,  54 
Laplace,  130 
LarchevSque,  on  lunar  influence 

on  vegetation,  137 
Latourte,  on  lunar  influence  on 

animal  life,  172 
Leibnitz  Mountains,  116 


Libration,  1 1 8 
Lieutaud,  168 
Lohrmann,  62,  63,  in 
Louis  XI,  156 
Louis  XIII,  167 
Louis  XIV,  167 
Louis  XVIII,  129 

Madler,  116.     See  Beer 

Manginus,  87,  116 

Marsh  of  Fogs,  1 10 

Maurolycus,  87,  88,  116 

Mayer's  map,  59 

Mead,  175 

Menuret,  175 

Messier,  1 1 1 

Millochau,  1 1 1 

Mont  Blanc,  1 10 

Moon,  theories  of  the  ancients, 
8  ;  Galileo's  discoveries,  10  ; 
relations  with  the  earth  as  its 
satellite,  28  ;  origin  of,  29  ; 
always  presents  the  same  side 
to  the  earth,  31  ;  phases,  33  ; 
obliquityof  orbit,  38;  apparent 
size  of  disc,  38  ;  distance,  47, 
74  ;  movements,  47  ;  nomen- 
clature of  its  mountains  and 
"  seas,"  57,  58  ;  lunar  land- 
scapes, 82  ;  volcanoes  and 
mountain  rings,  83  ;  the  lunar 
day,  89  ;  colour  on  the  Moon, 
94  ;  visibility  of  lunar  ob- 
jects, 99  ;  action  of  gravita- 
tion on,  104  ;  theory  of  its 
surface  formations,  113;  libra- 
tion,  118;  action  on  the 
tides,  1 20 ;  alleged  influence  on 
the  weather,  124  ;  question  of 
lunar  action  on  vegetable  life, 
137  ;  and  on  animal  life,  171  ; 
suggestions  for  the  study  of 
the  Moon,  179,  180,  182,  183, 
190 ;  lunar  elements  (table 
of),  192  ;  list  of  lunar  "seas," 
195  ;  mountain  chains,  196 

Morinus,  167 

Muller,  Johann.  See  Regio- 
montanus 


INDEX 


199 


Napoleon,  169 

Nasmyth  and  Carpenter,  work 

on  the  Moon,  63 
Nelson,  63,  64 
Newton,  46,  104,  106 

Ocean  of  Storms,  92 

Petavius,  87 
Piso,  175 
Plato,  in 
Pliny,  19,  23 
Plutarch,  9 
Ptolemy,  20 
Ptolemy,  113,  115 
Ptolemy     Euergetes     and     the 
pharos  of  Alexandria,  25 

Regiomontanus,  157 

Rheita,  de,  his  map  of  the  Moon, 

Si.  S3 

Riccioli's   map   and    system  of 
lunar  nomenclature,  57 

Scheiner,  54 
Schmidt's  map,  63,  64 
Schroeter,  61,  i  n 
Schroeter,  116,  182 
Sea  of  Crises,  113 


Sea  of  Mists,  115 
Sea  of  Rains,  108,  113 
Sea  of  Serenity,  1 1 1 ,  113 
Sea  of  Vapours,  109 
Seneca,  20 
Stoefler,  158 
Stoefler,  88,  116 
Straight  Range,  115,  181 

Tatius,    Achilles.     See   Achilles 

Tatius. 

Telescope,  invention  of,  10 
Thales,  34 
Theatetus,  no,  112 
Theophilus,  113 
Tides,  1 20 
Torricelli,  124 
Triesnecker,  114 
Tycho,  113,  114,  116 
Tycho  Brahe,  159 

Virgil,  153 
Voltaire,  167 

Wagner,  William,  74 

Weineck,  102 

Wells,  H.  G.,  and  the   "Time 

Machine,"  97 
Wolf  Mountains,  no 


PRINTED    BY 

ILA7ELL,    WATSON   AND    VINKT,    tO. , 
LONDON  AND   AYLKSBURY. 


UC  SOUTHERN  REGIONAL  LIBRARY  FACILITY 


A    000  1 57  480     5 


